Oxford University Press
Nucleic Acids Research, Vol. 19, No. 22 6327
Nucleotide sequences of new members (H3-lV and H3-V) of the chicken H3 histone-encoding gene family Yoshiko Setoguchi and Tatsuo Nakayama Department of Biochemistry, Miyazaki Medical College, Kiyotake, Miyazaki 889-16, Japan EMBL accession nos X62291 and X62292
Submitted October 14, 1991 The chicken H3 gene family consists of nine highly homologous members (H3-I to H3-IX), which fall into two major histone gene clusters (1, 2). Of the nine genes, only the three (H3-I, H3-ll and H3-Ill) have been sequenced (3, 4). To understand how expression of each H3 gene is regulated, it is essential to know the complete nucleotide sequences including the 5'-flanking and 3'-flanking regions of all of the genes. Here we report the nucleotide sequences of H3-IV (EMBL accession no. X62291) and H3-V (EMBL accession no. X62292), which belong to the major histone gene cluster containing H3-I (3) but not to another gene cluster containing H3-ll and H3-Ifl (4). The new members are located in inverted orientations and share 531 bp 3' nontranslated flanking region. The coding regions of H3-IV and H3-V, like those of the three previously sequenced H3 genes (3, 4), are 408 bp long and code for a protein composed of 136 amino acids including a putative initiation Met. These five H3 genes all code for the same amino acid sequence, whereas they differ in coding sequence by 2 to 7 bp each. To clarify whether the chicken H3 subfamily, like the human subfamily carrying three H3 protein variants (5), consists of several different protein variants or not, the nucleotide sequences of the remaining H3 genes must be characterized. When the 5'-flanking regions of the five H3 genes are compared, the nucleotide sequences of H3-IV and H3-V are seen to be the same up to nucleotide position -414 but to be different from those of the other three H3 genes (3, 4), At nucleotide positions -192 to - 181, H3-IV and H3-V possess overlapped copies of the possible Spl-binding element (6) of the form 5'-GGGCGGG-3', which is also located within the 5'-flanking region of H3-llI (4), in addition to the common CCAAT and TATA boxes. The analysis of the 3'-flanking sequences reveals that H3-IV and H3-V, like the common histone-encoding genes of higher eukaryotes, contain the histone-specific stem-loop and spacer elements, which possibly function as termination/ processing signals in nonpolyadenylated histone mRNAs (7).
Interestingly, the element of the form 5'-CGAGTCTG-3' is located at nucleotide positions +614 to +621 within the 3'-flanking region of H3-V but not within those of the other H3 genes. The octamer sequence differs by only one nucleotide from the consensus AP-1-binding sequence (8) of the form 5'-CGAGTCAG-3', which is found within the 5'-flanking regions of H3-ll, a member of the previously sequenced chicken H3 genes (4), and the replication-dependent hamster H3.2 gene (9). In the case of the H3.2 gene, the proteins interacting with the promoter at the octamer element (sequence X) have been identified as Junrelated proteins that could possibly contribute to the high-level expression of the gene (9). In addition, it is recently reported that a common transcriptional activator element is located in the coding regions of the replication-dependent mouse H2A and H3 genes (10). These findings suggest that the possible AP-l-binding element involved in the 3'-flanking region of the chicken H3-V gene has an effect on expression of the gene.
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