An alternative pathway of histone mRNA 3' end formation in mouse round spermatids.
During mammalian spermiogenesis, the post-meiotic stage of spermatogenesis, histones are replaced by protamines on the DNA. Despite this histone elimination, novel polyadenylated histone transcripts were detected in mouse round spermatids. Sequence analysis of a spermatid-specific H2a cDNA clone indicated that it was derived from a mRNA of a replication-dependent histone gene even though its transcript was not polyadenylated in somatic and earlier spermatogenic cells. In round spermatids, both the hairpin and purine-rich elements in the 3' untranslated region of the somatic pre-mRNA were retained in the mature poly(A)+ mRNA transcripts. Polyadenylation occurred downstream of the purine-rich element and was not preceded by the somatic AATAAA polyadenylation signal sequence. While polyadenylated histone transcripts from replication-dependent genes have been observed previously in somatic cells, characteristics of this type of 3'-end formation in mammalian round spermatids were unique. In particular, a specific replication-dependent H2a gene was transcribed either as a polyadenylated or non-polyadenylated transcript in these cells, suggesting that the type of transcript present was dependent on the RNA sequence. Finally, both poly(A)- and poly(A)+ mRNAs were found on polyribosomes from round spermatids, indicating that histones were being translated in these cells and that the polyadenylation status of these transcripts did not affect their translatability.
Moss
S B
SB
Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia 19104.
Ferry
R A
RA
Groudine
M
M
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D004261:DNA Replication; D018076:DNA, Complementary / Q000737:chemistry; D006657:Histones / Q000235:genetics*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D011061:Poly A / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000737:chemistry; D013087:Spermatids / Q000378:metabolism*; D014158:Transcription, Genetic
D018076:DNA, Complementary; D006657:Histones; D012333:RNA, Messenger; D011061:Poly A