Chicken histone H5 mRNA: the polyadenylated RNA lacks the conserved histone 3′ terminator sequence

Abstract

Using 3 overlapping cDNA clones we have determined the nucleotide sequence of chicken histonq H5 mRNA. The mRNA does not contain the 23 base conserved sequence element' that is present at the 3' end of cell-cycle regulated histone mRNAs. Although the RNA is polyadenylated it lacks the 3' AAUAAA sequence. I NTRODUCT IONHistones Hl and H5 share common structural features2 and occupy similar positions, outside the nucleosome, in chromatin structure3 Observed similarities between the primary sequences of the HI and H5 proteins have led to the suggestion that the genes coding for Hl and H5 may be related4.However, a number of observations indicate that Hl and H5 may not be as closely related as the protein sequence data would imply. Unlike the majority of the histone rRNAs, which lack a poly-A tail5, H5 mRNA has been shown to be polyadenylated6, and while H5 may be synthesized in the nondividing reticulocyte7, the expression of the major classes of histones, including Hl, appears to be closely coupled to DNA synthesis8'9.In this paper we present the nucleotide sequence of H5 mRNA. The determination of the structure of H5 mRNA and the analysis of features of the nucleotide sequence should help to clarify the relationship of H5 to the other cell-cycle regulated histone genes. MATERIALS AND METHODSSizing of H5 mRNA. Total chick embryo RNA (20 ,g), prepared by the guanidine-HCl extraction procedure10, was electrophoresed in the presence of 10 mM methyl mercury hydroxide in 1.5% agarose gels, as described by Bailey and Davidson1. The gels were treated with mercaptoethanol, stained C I R L Press Limited, Oxford, England. 6777

Expression of replication-dependent histone genes in avian spermatids involves an alternate pathway of mRNA 3'-end formation.

“…Since the transcripts of several replication-independent replacement and tissue-specific variant histone genes in somatic cells are polyadenylated (20,27,32) by hybridizing the filters with a 32P-labeled glyceraldehyde-3-phosphate dehydrogenase probe from pGAD-28 (19). Autoradiograms of lanes 6 and 7 were exposed two times longer than autoradiograms of lanes 1 to 5.…”

“…Promoter elements that are necessary for the increase in transcription during the S phase, such as AAGAAACACA for Hi replication-dependent genes, are not found in replacement variant promoters. Replacement variant transcripts are polyadenylated and lack the terminal hairpin structure that is required for both the 3' processing and regulated degradation of replication-dependent mRNAs (20,27,32). Introns occur in replacement variant genes (9, 27, 32), but have never been observed in replication-dependent genes.…”

“…Replacement variant transcripts are polyadenylated and lack the terminal hairpin structure that is required for both the 3' processing and regulated degradation of replication-dependent mRNAs (20,27,32). Introns occur in replacement variant genes (9,27,32), but have never been observed in replication-dependent genes. Finally, replication-dependent genes are clustered together in the genome (17,23), while replacement variant genes are dispersed.…”

The stem-loop structure at the 3' end of histone mRNA is necessary and sufficient for regulation of histone mRNA stability.

“…This distinctive stem-loop structure is present at the 3' end of all histone mRNAs which are expressed coordinately with DNA synthesis but is lacking in those histone mRNAs which are expressed constituitively (e.g., H3.3 [23]) or independently of DNA synthesis (e.g., H5 [10,13]). The H3.3 mRNA concentrations are not affected by inhibition of DNA synthesis (4,18).…”

Expression of mouse histone genes: transcription into 3' intergenic DNA and cryptic processing sites downstream from the 3' end of the H3 gene.

“…The histone mRNAs of yeast (13) and tetrahymena (4) are poly(A)+ as are some of the histone mRNAs in Xenopus eggs (3,26), although the same genes give rise to nonpoly(A)+ mRNAs in Xenopus embryos (3). Histone mRNA for chicken histone H5 is also poly(A)+ (24) and lacks the hairpin loop structure (19). The replacement-variant histone H3.3 does not show the same regulation of mRNA degradation as the replicationvariant histones H3.1 and H3.2 (28).…”