Expression of replication-dependent histone genes in avian spermatids involves an alternate pathway of mRNA 3'-end formation.
In somatic cells the expression of replication-dependent histone genes is coupled to the S phase of the cell cycle. However, we have found a number of novel H2a, H2b, and H3 poly(A)+ RNA species in avian haploid round spermatids. The spermatid-specific H2a and H2b 0.8-kilobase RNAs are transcribed from a subset of the replication-dependent H2a and H2b gene families. Two cDNAs derived from the spermatid-specific H2b transcripts were isolated and sequenced. The structures of these cDNAs reveal that the spermatid-specific RNAs are identical to the 0.5-kilobase poly(A)- H2b mRNAs expressed in proliferating somatic cells, except for the addition of poly(A) at the 3' ends. The site of poly(A) addition in the spermatid-specific RNAs is located 26 to 28 nucleotides 3' of the poly(A)- H2b mRNA terminus. Thus, the hairpin structures and purine-rich elements required for the U7 small nuclear ribonucleoprotein-mediated cleavage reaction that generates the 3' ends of poly(A)- H2b mRNAs are not utilized in spermatids and are retained in the poly(A)+ H2b RNAs.
Challoner
P B
PB
Department of Genetics, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Moss
S B
SB
Groudine
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle; D002645:Chickens; D004247:DNA / Q000235:genetics; D004261:DNA Replication; D005786:Gene Expression Regulation; D006657:Histones / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D011061:Poly A / Q000235:genetics; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics*; D013087:Spermatids / Q000166:cytology / Q000378:metabolism
D006657:Histones; D012333:RNA, Messenger; D011061:Poly A; D012313:RNA; D004247:DNA