OOl:J-7‘227/92/1314-1583$03.00/O Endocrmology Copyright 0 1992 by The Endocrine
Society
Remembrance: and Receptors
: -, ,0 75
th
YEAR
Vol. 131, No. 4 Printed in USA.
The Introduction of Molecular Biology into the Study of Hormone Action
The roots of molecular biology date back to the early 1950s when studies of nucleic acid chemistry led to the first structural models of DNA, and genetic studies of bacteria led to our first models of regulation of gene expression. Endocrinology, at that time, was fixated on the previous decade’s discoveriesof the metabolic enzymes and the role of cofactors in regulating intermediary metabolism. In particular, steroid hormones were studied as metabolic substrates that were expected to have critical metabolites, which in turn were likely to be cofactors in an essentialmetabolic pathway. The culmination of this line of reasoning came in the form of the steroid-dependent transhydrogenase theory of the late 1950s. This theory proposed that hormonal steroids acted as oxidation-reduction cofactors in the transfer of reducing equivalents from NADH to NADP. Whereas there were some reservations expressedabout the transhydrogenase theory, it was generally accepted as explaining the biological response to estrogensand other steroids. Two new lines of steroid hormone research, represented by a small minority of investigators, also were underway in the 1950s. The research of these investigators was to lead to the demise of the transhydrogenase theory and to the development of current models of steroid hormone action. Studies of tissue and cell uptake of steroid hormones had been hindered by the low specific activity of the radioactive Cl4 steroids; all that were available at the time. This in turn necessitated the use of large, nonphysiological dosesof the steroid in either animals or tissue incubations. The introduction of tritium-labeled steroids had a major impact on steroid hormone research. Preparing and counting tritiated compounds in the 1950s was no trivial matter. This predated commercial sourcesof tritiated compounds, and scintillation counters were just in the development stages.Elwood Jensen was a young organic chemist in the Ben May Laboratories at the University of Chicago who incorporated the available techniques of tritiating and counting estrogenic steroids, which made these early studies of hormone action possible. Jensen’sstudies, in conjunction with H. Jacobsonand others, were undertaken when receptors were only a theoretical concept that pharmacologists talked about but for which there were no experimental observations (1). No one had actually studied directly a receptor of any kind up to that time. For example, the research model for neurotransmitter receptors in the 1950s and the 1960s was the enzyme acetylcholine esterase.As mentioned above, the steroids were also thought to function by interacting with other enzymes. Received April 1, 1992. “Remembrance” articles discuss people and events as remembered the author. The opinion(s) expressed are solely those of the writer do not reflect the view of the Journal or The Endocrine Society.
by and
Into this scientific scene came the first of Jensen’sreports, a paper presented at the 1958 International Biochemistry meetingsin Vienna. Jensen’spaper was delivered in a session of short reports. It is ironic that Jensen’spaper was scheduled concurrently with a major symposium on steroid hormones and transhydrogenases. Obviously, everyone who worked on steroid hormones was at the symposium except for a small band (five) of Elwood’s friends who showed up for his presentation. Those five listeners heard the report that presaged the demise of the transhydrogenase theory and introduced a new era in the study of steroid hormone action. These early studies of steroid hormone receptors laid the ground rules for all the hormone receptor studies that were to follow; thus Elwood Jensen and his colleagues were the creators of the modern concept of receptors. Another major thread of investigation beginning in the 1950swas the development of molecular biology. The Watson-crick structure of DNA and, perhaps more importantly, the Jacob, Monod, and Pardee studies of regulation of gene expressionin prokaryotes led to an early interest by a number of investigators in the regulation of gene expression in eukaryotes. Gerald Mueller of the McArdle Laboratories at the University of Wisconsin-Madison was one whose interest was aroused, and he immediately began to investigate certain aspectsof nucleic acid and protein synthesis in uterine tissue of the estrogen-stimulated rat (2). He and his associateswere able to demonstrate that estrogen markedly increasedoverall RNA synthesis within hours after estrogen treatment. They also found that protein synthesis increased early, suggesting that the entire gene expression system might be stimulated by estrogens.This led to the model of steroid hormone action presented by Mueller at the 1957 Laurentian Hormone Conference and reprinted here as Fig. 1. Mueller used the terminology of prokaryote gene expression; inducers, antiinducers, unmasking, etc., but it is clear that he had a vision that steroid hormones, by interacting with specific chromatin proteins, played a critical role in the processof gene regulation. A recurring problem with these early studies was the inability to work with specific proteins or gene products becauseof the lack of suitable methods. I can remember, as a postdoctoral fellow in Mueller’s laboratory, the morning when Gerry came into the laboratory highly excited by a paper he had read the evening before. The paper reported that a new antibiotic, Puromycin, was effective in blocking protein synthesis in animal cells. Mueller saw the potential of this inhibitor and used the antibiotic to block protein synthesis and all the known responsesto estrogen in uterine tissue (3). He thus demonstrated that specific responsesto estrogen depended on prior protein synthesis. This impli-
1583 The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 01:40 For personal use only. No other uses without permission. . All rights reserved.
1584
REMEMBRANCE
Endo. Voll31.
1992 No 4
FIG. 1. A scheme depicting possible sites of hormonal regulation of induced biosynthesis. T, Template, E, enzyme; 1, 2, or 3, possible sites of hormone action. (Reprinted with permission of the authors; Ref. 2.). Barrier
’
Inducer VI
Protelnt
Anti-inducw
Nucleic
7
\ Produc
cated estrogen as inducing the synthesis of specific proteins just as inducers did in bacterial cells, and led to later studies that showed estrogen induction of specific gene expression. In the 30 plus years since these investigations by Jensen’s and Mueller’s laboratories, their original ideas have been confirmed and extended in great measure. The extent of the receptor gene superfamily certainly has been a surprise and the complexity of gene expression regulation in animal cells was not predicted. However, these two pioneers made observations and predictions that served asmajor turning points for subsequentresearch into hormone action. Their influence also illustrates that scienceis not a democratic institution in which a majority vote is conclusive but rather is a continuing
Acid
+
1s
Activation or Inactivation of Enzyme
processin which minority positions can eventually prevail. Jack Gorski Department of Biochemistry and Animal Sciences University of Wisconsin Madison, Wisconsin References 1. Jensen EV, Jacobson HI 1960 Fate of steroid estrogens in target tissues. In: Pincus G, Vollner E (eds) Biological Activities of Steroids in Relation to Cancer. Academic Press, New York, pp 161-178 2. Mueller GC, Herranen AM, Jervell KF 1957 Studies on the mechanism of action of estrogens. Recent Prog Hormone Res 4:95-139 3. Mueller GC, Gorski J, Aizawa Y 1961 The role of protein synthesis in early estrogen action. Proc Nat1 Acad Sci USA 47:164-169
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 01:40 For personal use only. No other uses without permission. . All rights reserved.
Society
Remembrance: and Receptors
: -, ,0 75
th
YEAR
Vol. 131, No. 4 Printed in USA.
The Introduction of Molecular Biology into the Study of Hormone Action
The roots of molecular biology date back to the early 1950s when studies of nucleic acid chemistry led to the first structural models of DNA, and genetic studies of bacteria led to our first models of regulation of gene expression. Endocrinology, at that time, was fixated on the previous decade’s discoveriesof the metabolic enzymes and the role of cofactors in regulating intermediary metabolism. In particular, steroid hormones were studied as metabolic substrates that were expected to have critical metabolites, which in turn were likely to be cofactors in an essentialmetabolic pathway. The culmination of this line of reasoning came in the form of the steroid-dependent transhydrogenase theory of the late 1950s. This theory proposed that hormonal steroids acted as oxidation-reduction cofactors in the transfer of reducing equivalents from NADH to NADP. Whereas there were some reservations expressedabout the transhydrogenase theory, it was generally accepted as explaining the biological response to estrogensand other steroids. Two new lines of steroid hormone research, represented by a small minority of investigators, also were underway in the 1950s. The research of these investigators was to lead to the demise of the transhydrogenase theory and to the development of current models of steroid hormone action. Studies of tissue and cell uptake of steroid hormones had been hindered by the low specific activity of the radioactive Cl4 steroids; all that were available at the time. This in turn necessitated the use of large, nonphysiological dosesof the steroid in either animals or tissue incubations. The introduction of tritium-labeled steroids had a major impact on steroid hormone research. Preparing and counting tritiated compounds in the 1950s was no trivial matter. This predated commercial sourcesof tritiated compounds, and scintillation counters were just in the development stages.Elwood Jensen was a young organic chemist in the Ben May Laboratories at the University of Chicago who incorporated the available techniques of tritiating and counting estrogenic steroids, which made these early studies of hormone action possible. Jensen’sstudies, in conjunction with H. Jacobsonand others, were undertaken when receptors were only a theoretical concept that pharmacologists talked about but for which there were no experimental observations (1). No one had actually studied directly a receptor of any kind up to that time. For example, the research model for neurotransmitter receptors in the 1950s and the 1960s was the enzyme acetylcholine esterase.As mentioned above, the steroids were also thought to function by interacting with other enzymes. Received April 1, 1992. “Remembrance” articles discuss people and events as remembered the author. The opinion(s) expressed are solely those of the writer do not reflect the view of the Journal or The Endocrine Society.
by and
Into this scientific scene came the first of Jensen’sreports, a paper presented at the 1958 International Biochemistry meetingsin Vienna. Jensen’spaper was delivered in a session of short reports. It is ironic that Jensen’spaper was scheduled concurrently with a major symposium on steroid hormones and transhydrogenases. Obviously, everyone who worked on steroid hormones was at the symposium except for a small band (five) of Elwood’s friends who showed up for his presentation. Those five listeners heard the report that presaged the demise of the transhydrogenase theory and introduced a new era in the study of steroid hormone action. These early studies of steroid hormone receptors laid the ground rules for all the hormone receptor studies that were to follow; thus Elwood Jensen and his colleagues were the creators of the modern concept of receptors. Another major thread of investigation beginning in the 1950swas the development of molecular biology. The Watson-crick structure of DNA and, perhaps more importantly, the Jacob, Monod, and Pardee studies of regulation of gene expressionin prokaryotes led to an early interest by a number of investigators in the regulation of gene expression in eukaryotes. Gerald Mueller of the McArdle Laboratories at the University of Wisconsin-Madison was one whose interest was aroused, and he immediately began to investigate certain aspectsof nucleic acid and protein synthesis in uterine tissue of the estrogen-stimulated rat (2). He and his associateswere able to demonstrate that estrogen markedly increasedoverall RNA synthesis within hours after estrogen treatment. They also found that protein synthesis increased early, suggesting that the entire gene expression system might be stimulated by estrogens.This led to the model of steroid hormone action presented by Mueller at the 1957 Laurentian Hormone Conference and reprinted here as Fig. 1. Mueller used the terminology of prokaryote gene expression; inducers, antiinducers, unmasking, etc., but it is clear that he had a vision that steroid hormones, by interacting with specific chromatin proteins, played a critical role in the processof gene regulation. A recurring problem with these early studies was the inability to work with specific proteins or gene products becauseof the lack of suitable methods. I can remember, as a postdoctoral fellow in Mueller’s laboratory, the morning when Gerry came into the laboratory highly excited by a paper he had read the evening before. The paper reported that a new antibiotic, Puromycin, was effective in blocking protein synthesis in animal cells. Mueller saw the potential of this inhibitor and used the antibiotic to block protein synthesis and all the known responsesto estrogen in uterine tissue (3). He thus demonstrated that specific responsesto estrogen depended on prior protein synthesis. This impli-
1583 The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 01:40 For personal use only. No other uses without permission. . All rights reserved.
1584
REMEMBRANCE
Endo. Voll31.
1992 No 4
FIG. 1. A scheme depicting possible sites of hormonal regulation of induced biosynthesis. T, Template, E, enzyme; 1, 2, or 3, possible sites of hormone action. (Reprinted with permission of the authors; Ref. 2.). Barrier
’
Inducer VI
Protelnt
Anti-inducw
Nucleic
7
\ Produc
cated estrogen as inducing the synthesis of specific proteins just as inducers did in bacterial cells, and led to later studies that showed estrogen induction of specific gene expression. In the 30 plus years since these investigations by Jensen’s and Mueller’s laboratories, their original ideas have been confirmed and extended in great measure. The extent of the receptor gene superfamily certainly has been a surprise and the complexity of gene expression regulation in animal cells was not predicted. However, these two pioneers made observations and predictions that served asmajor turning points for subsequentresearch into hormone action. Their influence also illustrates that scienceis not a democratic institution in which a majority vote is conclusive but rather is a continuing
Acid
+
1s
Activation or Inactivation of Enzyme
processin which minority positions can eventually prevail. Jack Gorski Department of Biochemistry and Animal Sciences University of Wisconsin Madison, Wisconsin References 1. Jensen EV, Jacobson HI 1960 Fate of steroid estrogens in target tissues. In: Pincus G, Vollner E (eds) Biological Activities of Steroids in Relation to Cancer. Academic Press, New York, pp 161-178 2. Mueller GC, Herranen AM, Jervell KF 1957 Studies on the mechanism of action of estrogens. Recent Prog Hormone Res 4:95-139 3. Mueller GC, Gorski J, Aizawa Y 1961 The role of protein synthesis in early estrogen action. Proc Nat1 Acad Sci USA 47:164-169
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 01:40 For personal use only. No other uses without permission. . All rights reserved.
