PROFILE
PROFILE
Profile of Alberto Kornblihtt Jennifer Viegas Science Writer
Molecular biologist Alberto Kornblihtt is proud to work within a tightly knit group of Buenos Aires-based researchers who are studying ribonucleic acids. Kornblihtt and his team investigate the regulation of alternative RNA splicing, a process that affects nearly 90% of human genes. Kornblihtt, who was elected as a foreign associate of the National Academy of Sciences in 2011, was one of the first scientists to document how a single transcribed gene can give rise to different messenger RNAs that allow the gene to express different proteins. Because mutations that affect alternative splicing are a source of human disease, the findings of Kornblihtt and his colleagues reveal mechanisms underlying hereditary diseases, premature aging, and cancer. Family of Teachers
Kornblihtt was born in 1954 in the city he still calls home, Buenos Aires. “My father was a civil engineer who loved and taught mathematics,” he says. “My mother was a high school teacher in geography. My oldest sister was a computer scientist, and my other sister was a kindergarten teacher, so the love for knowledge and education was constantly present in my childhood.” As a child,
adds. “His wife, Professor Mirtha Flawiá, was also very important in the development of my early career. She was very enthusiKornblihtt also enjoyed painting, drawing, astic in supporting young scientists in the and playing with anything mechanical. He lab to explore new research avenues.” says, “I always knew that I was going to be One Gene, Many Proteins a scientist, but I had no idea in what field.” From 1981 to 1984, Kornblihtt was a postKornblihtt’s choice of scientific field gained doctoral researcher at the Sir William clarity in 1970, when he was a student at the Dunn School of Pathology in Oxford. With Colegio Nacional de Buenos Aires, a public Professor Francisco “Tito” Baralle, Kornblihtt high school run by the University of Buenos cloned the human fibronectin gene and Aires. During that year, 16-year-old Kornblihtt found that the gene was alternatively took a botany and biology class given by spliced (1). The research demonstrated that plant taxonomist Rosa Guaglianone. “She a single gene could generate at least 10 was exceptional,” he says. “We did labora- polypeptides, which are chains of amino tory and microscope work and learned acid molecules that make up proteins. about DNA, mRNA, proteins, and the geUntil this and subsequent studies, alternetic code. It was an exciting experience native splicing was poorly understood. It is that marked me for the rest of my life.” now known to be a major contributor to Kornblihtt continued his studies at the protein diversity. Kornblihtt explains, “AlUniversity of Buenos Aires, where he majored ternative splicing is a variation of splicing in in biology and graduated in 1977. During which each precursor messenger RNA (prehis doctoral thesis work in biochemistry at mRNA) molecule can give rise to different the Campomar Foundation, his primary mature mRNAs, depending on which segmentor was Héctor Torres. “He was a ments are joined and which are excised.” The disciple of Luis Leloir,” Kornblihtt says, ribosome then “reads” the coding instrucreferring to the Argentine physician and bio- tions of the mRNAs and synthesizes different chemist Leloir, who received a Nobel Prize proteins. for discovering sugar nucleotides. “Torres’ Coupled Splicing and Transcription passion for discovery was contagious,” he Kornblihtt moved back to Argentina in 1984. He became a professor of molecular and cell biology at the Facultad de Ciencias Exactas y Naturales at the University of Buenos Aires, where he remains. Soon thereafter, he began to assemble a team of researchers to study the regulation of alternative pre-mRNA splicing. A seminal achievement happened just over a decade later when, in 1997, Kornblihtt and his colleagues proved that promoters—DNA sequences that define where transcription of a gene begins—affect alternative splicing (2). Transcription is the process by which the information in a strand of DNA is copied into a new molecule of mRNA. Kornblihtt says, “This was the first evidence that transcription and splicing are not independent events, but that the outcome of splicing depends on the parameters of transcription.” His team has since determined that this functional coupling of splicing and transcription This is a Profile of a recently elected member of the National Academy of Sciences to accompany the member’s Inaugural Article
Alberto Kornblihtt. Image courtesy of Oliver Kornblihtt. www.pnas.org/cgi/doi/10.1073/pnas.1421075111
on page 15622 in issue 44 of volume 111.
PNAS Early Edition | 1 of 2
Argonaute proteins, which are involved in human organ growth and development, are
known to play a role in posttranscriptional regulation in the cell’s cytoplasm. Kornblihtt’s Inaugural Article describes how these proteins also affect gene expression in the nucleus during transcription (10). In particular, the paper provides evidence that Argonaute proteins can bind to specific locations in the genome. These locations are transcriptional enhancers, regions in the DNA that control the expression of one or multiple genes by governing when these genes must be turned on or off. Aberrant activation or silencing of these enhancers can affect cell function and lead to cancer. “These results contribute to the understanding of the complex regulation of gene expression in eukaryotic cells,” Kornblihtt and his colleagues report. In addition to his position as Plenary Professor at the Department of Physiology, Molecular, and Cell Biology at the University of Buenos Aires, Kornblihtt is Director of the Institute of Physiology, Molecular Biology, and Neurosciences of the Argentine Research Council, and has been an International Research Scholar of the Howard Hughes Medical Institute since 2002. He has won several awards, including a Guggenheim Fellowship (1991), Investigator of the Argentine Nation Prize, granted by the President of Argentina (2010), Foreign Membership in the European Molecular Biology Organization (2012), and Diamond Award for the most relevant scientist of Argentina of the decade, ex aequo with physicist Juan Martín Maldacena (2013). Kornblihtt teaches an introductory course on molecular biology at the University of Buenos Aires. As he continues to inspire the next generation of Argentine scientists, Kornblihtt explains that he is part of a continuum, carrying on a long tradition of scientific achievers in Argentina that began with Leloir and physiologist and Nobel Laureate Bernardo Houssay.
1 Kornblihtt AR, Umezawa K, Vibe-Pedersen K, Baralle FE (1985) Primary structure of human fibronectin: differential splicing may generate at least 10 polypeptides from a single gene. EMBO J 4(7): 1755–1759. 2 Cramer P, Pesce CG, Baralle FE, Kornblihtt AR (1997) Functional association between promoter structure and transcript alternative splicing. Proc Natl Acad Sci USA 94(21): 11456–11460. 3 de la Mata M, et al. (2003) A slow RNA polymerase II affects alternative splicing in vivo. Mol Cell 12(2):525–532. 4 de la Mata M, Kornblihtt AR (2006) RNA polymerase II C-terminal domain mediates regulation of alternative splicing by SRp20. Nat Struct Mol Biol 13(11):973–980. 5 Schor IE, Rascovan N, Pelisch F, Alló M, Kornblihtt AR (2009) Neuronal cell depolarization induces intragenic chromatin
modifications affecting NCAM alternative splicing. Proc Natl Acad Sci USA 106(11):4325–4330. 6 Alló M, et al. (2009) Control of alternative splicing through siRNAmediated transcriptional gene silencing. Nat Struct Mol Biol 16(7): 717–724. 7 Schor IE, Fiszbein A, Petrillo E, Kornblihtt AR (2013) Intragenic epigenetic changes modulate NCAM alternative splicing in neuronal differentiation. EMBO J 32(16):2264–2274. 8 Muñoz MJ, et al. (2009) DNA damage regulates alternative splicing through inhibition of RNA polymerase II elongation. Cell 137(4): 708–720. 9 Petrillo E, et al. (2014) A chloroplast retrograde signal regulates nuclear alternative splicing. Science 344(6182):427–430. 10 Alló M, et al. (2014) Argonaute-1 binds transcriptional enhancers and controls constitutive and alternative splicing in human cells. Proc Natl Acad Sci USA 111(44):15622–15629.
reported a strategy to modify chromatin structure at specific points in a gene by using small noncoding RNAs (6). The researchers also discovered the mechanism by which changes in nerve cell activity and neuron differentiation, which can relax or tighten chromatin structure, promote changes in transcriptional elongation (7). Those alterations affect alternative splicing of genes essential for neuronal function. The team’s chromatin-related studies have contributed to the emerging field concerning the relationship between epigenetics (the study of changes in organisms caused by modification of gene expression rather than alteration of the DNA sequence itself) and splicing. UV-Induced DNA Damage
The image illustrates the new emerging nuclear roles for the Argonaute 1 protein, represented in the center of the picture as its cephalopodan alter ego. Nucleosomes (in red) are marked by specific histone modifications (light green). Argonaute 1 binds to intragenic transcriptional enhancers through interactions with enhancer RNAs, and is able to affect gene regulation during transcription performed by RNA polymerase II (olive green) at the level of splicing of exons and introns depicted in light cream color. Digital illustration courtesy of Amagoia Agirre.
occurs through two nonmutually exclusive mechanisms: the control of transcriptional elongation speed (kinetic coupling) (3) and the association of splicing factors to RNA polymerase II, an enzyme that catalyzes the transcription of DNA to synthesize premRNA (recruitment coupling) (4). Kornblihtt says, “DNA is not naked in the nucleus.” It is instead associated with histone proteins to form chromatin, which composes the chromosomes of organisms other than bacteria. Chromatin structure, which affects RNA polymerase elongation rates and alternative splicing, has therefore been another focus of research for Kornblihtt and his colleagues. In 2009, they presented some of the first evidence supporting that chromatin structure affects alternative splicing by regulating the speed of transcription (5). The same year, Kornblihtt and his colleagues also
2 of 2 | www.pnas.org/cgi/doi/10.1073/pnas.1421075111
In another line of investigation, Kornblihtt and his team discovered the cellular mechanism by which DNA damage caused by UV light (UV) irradiation affects alternative splicing (8). This mechanism is key to understanding how skin cells respond to UV light contained in sunlight. Kornblihtt and his colleagues found that after DNA is damaged by UV irradiation, the cell responds by adding new phosphate groups to the RNA polymerase enzyme. This slows down the enzyme, thereby affecting the alternative splicing “decisions” of many genes. Kornblihtt explains, “This promotes the death of the cells carrying the damaged DNA, preventing the proliferation of mutated cells that could eventually become cancer cells.” While the team’s studies are largely focused on human cells in culture, they have recently extended their work to plants. The researchers have shown that light and dark conditions modulate alternative splicing through signals that go from the chloroplast to the nucleus (9). Argonaute Proteins and Gene Regulation
Viegas
PROFILE
Profile of Alberto Kornblihtt Jennifer Viegas Science Writer
Molecular biologist Alberto Kornblihtt is proud to work within a tightly knit group of Buenos Aires-based researchers who are studying ribonucleic acids. Kornblihtt and his team investigate the regulation of alternative RNA splicing, a process that affects nearly 90% of human genes. Kornblihtt, who was elected as a foreign associate of the National Academy of Sciences in 2011, was one of the first scientists to document how a single transcribed gene can give rise to different messenger RNAs that allow the gene to express different proteins. Because mutations that affect alternative splicing are a source of human disease, the findings of Kornblihtt and his colleagues reveal mechanisms underlying hereditary diseases, premature aging, and cancer. Family of Teachers
Kornblihtt was born in 1954 in the city he still calls home, Buenos Aires. “My father was a civil engineer who loved and taught mathematics,” he says. “My mother was a high school teacher in geography. My oldest sister was a computer scientist, and my other sister was a kindergarten teacher, so the love for knowledge and education was constantly present in my childhood.” As a child,
adds. “His wife, Professor Mirtha Flawiá, was also very important in the development of my early career. She was very enthusiKornblihtt also enjoyed painting, drawing, astic in supporting young scientists in the and playing with anything mechanical. He lab to explore new research avenues.” says, “I always knew that I was going to be One Gene, Many Proteins a scientist, but I had no idea in what field.” From 1981 to 1984, Kornblihtt was a postKornblihtt’s choice of scientific field gained doctoral researcher at the Sir William clarity in 1970, when he was a student at the Dunn School of Pathology in Oxford. With Colegio Nacional de Buenos Aires, a public Professor Francisco “Tito” Baralle, Kornblihtt high school run by the University of Buenos cloned the human fibronectin gene and Aires. During that year, 16-year-old Kornblihtt found that the gene was alternatively took a botany and biology class given by spliced (1). The research demonstrated that plant taxonomist Rosa Guaglianone. “She a single gene could generate at least 10 was exceptional,” he says. “We did labora- polypeptides, which are chains of amino tory and microscope work and learned acid molecules that make up proteins. about DNA, mRNA, proteins, and the geUntil this and subsequent studies, alternetic code. It was an exciting experience native splicing was poorly understood. It is that marked me for the rest of my life.” now known to be a major contributor to Kornblihtt continued his studies at the protein diversity. Kornblihtt explains, “AlUniversity of Buenos Aires, where he majored ternative splicing is a variation of splicing in in biology and graduated in 1977. During which each precursor messenger RNA (prehis doctoral thesis work in biochemistry at mRNA) molecule can give rise to different the Campomar Foundation, his primary mature mRNAs, depending on which segmentor was Héctor Torres. “He was a ments are joined and which are excised.” The disciple of Luis Leloir,” Kornblihtt says, ribosome then “reads” the coding instrucreferring to the Argentine physician and bio- tions of the mRNAs and synthesizes different chemist Leloir, who received a Nobel Prize proteins. for discovering sugar nucleotides. “Torres’ Coupled Splicing and Transcription passion for discovery was contagious,” he Kornblihtt moved back to Argentina in 1984. He became a professor of molecular and cell biology at the Facultad de Ciencias Exactas y Naturales at the University of Buenos Aires, where he remains. Soon thereafter, he began to assemble a team of researchers to study the regulation of alternative pre-mRNA splicing. A seminal achievement happened just over a decade later when, in 1997, Kornblihtt and his colleagues proved that promoters—DNA sequences that define where transcription of a gene begins—affect alternative splicing (2). Transcription is the process by which the information in a strand of DNA is copied into a new molecule of mRNA. Kornblihtt says, “This was the first evidence that transcription and splicing are not independent events, but that the outcome of splicing depends on the parameters of transcription.” His team has since determined that this functional coupling of splicing and transcription This is a Profile of a recently elected member of the National Academy of Sciences to accompany the member’s Inaugural Article
Alberto Kornblihtt. Image courtesy of Oliver Kornblihtt. www.pnas.org/cgi/doi/10.1073/pnas.1421075111
on page 15622 in issue 44 of volume 111.
PNAS Early Edition | 1 of 2
Argonaute proteins, which are involved in human organ growth and development, are
known to play a role in posttranscriptional regulation in the cell’s cytoplasm. Kornblihtt’s Inaugural Article describes how these proteins also affect gene expression in the nucleus during transcription (10). In particular, the paper provides evidence that Argonaute proteins can bind to specific locations in the genome. These locations are transcriptional enhancers, regions in the DNA that control the expression of one or multiple genes by governing when these genes must be turned on or off. Aberrant activation or silencing of these enhancers can affect cell function and lead to cancer. “These results contribute to the understanding of the complex regulation of gene expression in eukaryotic cells,” Kornblihtt and his colleagues report. In addition to his position as Plenary Professor at the Department of Physiology, Molecular, and Cell Biology at the University of Buenos Aires, Kornblihtt is Director of the Institute of Physiology, Molecular Biology, and Neurosciences of the Argentine Research Council, and has been an International Research Scholar of the Howard Hughes Medical Institute since 2002. He has won several awards, including a Guggenheim Fellowship (1991), Investigator of the Argentine Nation Prize, granted by the President of Argentina (2010), Foreign Membership in the European Molecular Biology Organization (2012), and Diamond Award for the most relevant scientist of Argentina of the decade, ex aequo with physicist Juan Martín Maldacena (2013). Kornblihtt teaches an introductory course on molecular biology at the University of Buenos Aires. As he continues to inspire the next generation of Argentine scientists, Kornblihtt explains that he is part of a continuum, carrying on a long tradition of scientific achievers in Argentina that began with Leloir and physiologist and Nobel Laureate Bernardo Houssay.
1 Kornblihtt AR, Umezawa K, Vibe-Pedersen K, Baralle FE (1985) Primary structure of human fibronectin: differential splicing may generate at least 10 polypeptides from a single gene. EMBO J 4(7): 1755–1759. 2 Cramer P, Pesce CG, Baralle FE, Kornblihtt AR (1997) Functional association between promoter structure and transcript alternative splicing. Proc Natl Acad Sci USA 94(21): 11456–11460. 3 de la Mata M, et al. (2003) A slow RNA polymerase II affects alternative splicing in vivo. Mol Cell 12(2):525–532. 4 de la Mata M, Kornblihtt AR (2006) RNA polymerase II C-terminal domain mediates regulation of alternative splicing by SRp20. Nat Struct Mol Biol 13(11):973–980. 5 Schor IE, Rascovan N, Pelisch F, Alló M, Kornblihtt AR (2009) Neuronal cell depolarization induces intragenic chromatin
modifications affecting NCAM alternative splicing. Proc Natl Acad Sci USA 106(11):4325–4330. 6 Alló M, et al. (2009) Control of alternative splicing through siRNAmediated transcriptional gene silencing. Nat Struct Mol Biol 16(7): 717–724. 7 Schor IE, Fiszbein A, Petrillo E, Kornblihtt AR (2013) Intragenic epigenetic changes modulate NCAM alternative splicing in neuronal differentiation. EMBO J 32(16):2264–2274. 8 Muñoz MJ, et al. (2009) DNA damage regulates alternative splicing through inhibition of RNA polymerase II elongation. Cell 137(4): 708–720. 9 Petrillo E, et al. (2014) A chloroplast retrograde signal regulates nuclear alternative splicing. Science 344(6182):427–430. 10 Alló M, et al. (2014) Argonaute-1 binds transcriptional enhancers and controls constitutive and alternative splicing in human cells. Proc Natl Acad Sci USA 111(44):15622–15629.
reported a strategy to modify chromatin structure at specific points in a gene by using small noncoding RNAs (6). The researchers also discovered the mechanism by which changes in nerve cell activity and neuron differentiation, which can relax or tighten chromatin structure, promote changes in transcriptional elongation (7). Those alterations affect alternative splicing of genes essential for neuronal function. The team’s chromatin-related studies have contributed to the emerging field concerning the relationship between epigenetics (the study of changes in organisms caused by modification of gene expression rather than alteration of the DNA sequence itself) and splicing. UV-Induced DNA Damage
The image illustrates the new emerging nuclear roles for the Argonaute 1 protein, represented in the center of the picture as its cephalopodan alter ego. Nucleosomes (in red) are marked by specific histone modifications (light green). Argonaute 1 binds to intragenic transcriptional enhancers through interactions with enhancer RNAs, and is able to affect gene regulation during transcription performed by RNA polymerase II (olive green) at the level of splicing of exons and introns depicted in light cream color. Digital illustration courtesy of Amagoia Agirre.
occurs through two nonmutually exclusive mechanisms: the control of transcriptional elongation speed (kinetic coupling) (3) and the association of splicing factors to RNA polymerase II, an enzyme that catalyzes the transcription of DNA to synthesize premRNA (recruitment coupling) (4). Kornblihtt says, “DNA is not naked in the nucleus.” It is instead associated with histone proteins to form chromatin, which composes the chromosomes of organisms other than bacteria. Chromatin structure, which affects RNA polymerase elongation rates and alternative splicing, has therefore been another focus of research for Kornblihtt and his colleagues. In 2009, they presented some of the first evidence supporting that chromatin structure affects alternative splicing by regulating the speed of transcription (5). The same year, Kornblihtt and his colleagues also
2 of 2 | www.pnas.org/cgi/doi/10.1073/pnas.1421075111
In another line of investigation, Kornblihtt and his team discovered the cellular mechanism by which DNA damage caused by UV light (UV) irradiation affects alternative splicing (8). This mechanism is key to understanding how skin cells respond to UV light contained in sunlight. Kornblihtt and his colleagues found that after DNA is damaged by UV irradiation, the cell responds by adding new phosphate groups to the RNA polymerase enzyme. This slows down the enzyme, thereby affecting the alternative splicing “decisions” of many genes. Kornblihtt explains, “This promotes the death of the cells carrying the damaged DNA, preventing the proliferation of mutated cells that could eventually become cancer cells.” While the team’s studies are largely focused on human cells in culture, they have recently extended their work to plants. The researchers have shown that light and dark conditions modulate alternative splicing through signals that go from the chloroplast to the nucleus (9). Argonaute Proteins and Gene Regulation
Viegas
