Transcription of the histone H5 gene is not S-phase regulated.

The expression of the genes for several histones and pA-globin was examined in the chicken erythroid cell lineage. During the transition from CFU-(E) to the mature erythrocyte, histone H5 gradually increased fourfold in nuclei with little concomitant displacement of the Hi histones. This resulted in a 70% net increase in linker histone (Hi plus H5) content. The differential accumulation of H5 reflected (i) an increase in the transcriptional activity of the H5 gene occurring at the erythroblast stage, (ii) an apparent longer half-life of H5 mRNA, and (iii) a higher stability of the protein. Although the transcriptional activity of the histone genes (except H5) decreased with cell age, it was not tightly coupled to the S phase. On the other hand, the mRNA levels for these histones were tightly regulated during the cell cycle. Use of protein and DNA synthesis inhibitors indicated that the content of H5 mRNA was regulated at the posttranscriptional level by a control mechanism(s) differing from those for the other histones. Although the transcription rates of the H5 and pA_globin genes were comparable, differential accumulation of iA_globin mRNA led to a 30-to 170-fold-higher copy number of the pA-globin mRNA as the cell matured.

Section: Resultsmentioning

confidence: 99%

“…3) (14). In view of these properties, we examined the temporal relationship between the transcription of several histone genes (Hi, H3, H2A, and H5) and that of a gene for a differentiated cell product (_A-globin).…”

Section: Resultsmentioning

confidence: 99%

Regulation of histone and beta A-globin gene expression during differentiation of chicken erythroid cells.

Affolter¹,

Côté²,

Renaud³

et al. 1987

“…The replacement or basal histone gene variants (49) and avian histone H5 (7) are notable exceptions to this rule. The cell cycle regulation of histone mRNA expression has been investigated in several systems and is likely to involve changes in the rate of gene transcription (14,17,32), changes in mRNA stability (15,17,40), and structural features of the mRNA transcripts and their templates (4,25).…”

mentioning

confidence: 99%

Comparison of the structure and cell cycle expression of mRNAs encoded by two histone H3-H4 loci in Saccharomyces cerevisiae.

Cross

Smith

1988

The haploid genome of Saccharomyces cerevisiae contains two nonallelic sets of histone H3 and H4 gene pairs, termed the copy I and copy I loci. The structures of the mRNA transcripts from each of these four genes were examined by nuclease protection and primer extension mapping. For each gene, several species of mRNAs were identified that differed in the lengths of their S' and 3' untranslated regions. The cell cycle accumulation pattern of the H3 and H4 mRNAs was determined in cells from early-exponential-growth cultures fractionated by centrifugal elutriation. The RNA trnscripts from all four genes were regulated with the cell division cycle, and btanscripts from the nonallelic gene copies showed tight temporal coordination. Cell cycle regulation did not depend on selection of a particular histone mRNA transcript since the ratio of the multiple species from each gene remained the same across the division cycle. Quantitative measurements showed significant differences in the amounts of mRNA expressed from the two nonallelic gene sets. The mRNAs from the copy 11 H3 and H4 genes were five to seven times more abundant than the mRNAs from the copy I genes. There was no dosage compensation in the steady-state levels of mRNA when either set of genes was deleted. In particular, there was no increase in the amount of copy I H3 or H4 transcripts in cells in which the high-abundance copy II genes were deleted.For most classes of histone, gene expression is regulated in a cell-cycle-dependent fashion, with the maximal amount of histone RNA and protein synthesis occurring in late G1 or early S phase (28, 37). The replacement or basal histone gene variants (49) and avian histone H5 (7) are notable exceptions to this rule. The cell cycle regulation of histone mRNA expression has been investigated in several systems and is likely to involve changes in the rate of gene transcription (14,17,32), changes in mRNA stability (15,17,40), and structural features of the mRNA transcripts and their templates (4, 25).The core histone genes of budding yeast, Saccharomyces cerevisiae, are organized as duplicate H2A-H2B and H3-H4 gene pairs (43). The four nonallelic chromosomal gene sets are unlinked and, at each locus, the paired genes are divergently transcribed (19, 45). The DNA sequences of analogous genes are highly conserved within the coding regions, but the 5' and 3' untranslated regions are divergent. The yeast core histone genes show a typical cell-divisioncycle-dependent pattern of expression. Both the rate of synthesis of new histone (23, 24) and the appearance of histone mRNA are periodic in the division cycle (20). There appear to be several mechanisms regulating expression of the genes, and both transcriptional and posttranscriptional controls have been proposed for the H2A and H2B genes (18,26,32,33).In this paper, we report the structure and cell cycle pattern of accumulation of the yeast histone H3 and H4 genes. These experiments addressed several aspects of H3 and H4 gene expression. First, we determined the structures of...

“…One of the cell cycle-independent variants is the human H3.3, which has an intron and encodes polyadenylated mRNA (46). The best-known examples of cell type-specific histones are the avian erythrocyte-specific H5 (11,45) and the mammalian testis-specific histones (4,27). During spermatogenesis, testis-specific histones (TH1, TH2A, and TH2B) are synthesized in the mammalian testis in the absence of DNA replication, and these histones replace the corresponding somatic histones (6,27).…”

mentioning

confidence: 99%

S-phase-specific transcription regulatory elements are present in a replication-independent testis-specific H2B histone gene.

Hwang¹,

Chae²

1989

The testis-specific H2B histone (TH2B) gene is expressed in pachytene spermatocytes during meiotic prophase I in the absence of any significant DNA synthesis. Unlike somatic histones, synthesis of testis-specific histones is not affected by inhibitors of DNA synthesis. A genomic rat TH2B gene was cloned by using a DNA fragment derived from TH2B cDNA as a probe. Expression of the cloned TH2B was investigated by gene transfer experiments. From these studies, we found that the 5' upstream region of the cloned TH2B gene contained S-phase-specific transcription elements which regulated expression of a reporter gene in an S-phase-specific manner. The S-phase-regulatory element was found to be located in two regions containing CCAAT elements between -153 and -110 base pairs (bp) and an octamer element (ATTTGCAT) between -109 and -84 bp. The two regions were required for a maximal stimulation of transcription of the cloned TH2B gene in S phase. On the other hand, only the octamer element was reported be important for the S-phase-specific transcription of human H2B gene. Since the synthesis of the TH2B histone is independent of DNA synthesis and specific for pachytene spermatocytes in vivo, the presence of the S-phase-specific transcription regulatory elements in the TH2B gene is surprising.During S phase in most eucaryotic cells, newly replicated DNA is assembled into chromatin by histone proteins (36). Therefore, there is a great demand for histones during S phase, when DNA replication occurs. Cells meet the demand for histone proteins by two different mechanisms: increased expression of histone genes and stabilization of histone mRNAs during the S phase (19,29,30,35,41,44). In this manner, cells achieve more than a 10-fold increase in histone mRNA during the S phase. The coupling of histone and DNA synthesis has been well established, but the mechanism of coupling is not clearly understood. Recently attention has been focused on the molecular mechanisms of the cell cycle-dependent expression of histone genes and the stabilization of mRNAs during S phase. The S-phase-specific histone gene transcription appears to be regulated by cisacting DNA elements present 5' of histone genes (3,23,31,40,42). Also, histone mRNAs appear to have a sequence element(s) for stabilization of the mRNAs during the S phase of the cell cycle (1,7,29,39,44). The 3' noncoding region of the histone mRNA has a highly conserved hairpin structure that appears to influence S-phase-specific stability of histone mRNAs (7, 39, 44).There are histone variants which are cell cycle-independent and cell type specific. One of the cell cycle-independent variants is the human H3.3, which has an intron and encodes polyadenylated mRNA (46). The best-known examples of cell type-specific histones are the avian erythrocyte-specific H5 (11, 45) and the mammalian testis-specific histones (4, 27). During spermatogenesis, testis-specific histones (TH1, TH2A, and TH2B) are synthesized in the mammalian testis in the absence of DNA replication, and these histones replace ...