Related Experiment Videos
An alternative pathway of histone mRNA 3' end formation in mouse round spermatids
S B Moss1, R A Ferry, M Groudine
1Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia 19104.
Abstract:
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.
Insights
Novel polyadenylated histone transcripts were found in mouse round spermatids, even after histone elimination during spermiogenesis. This polyadenylation process in spermatids is unique and does not affect histone translation.
Area of Science:
- Reproductive biology
- Molecular genetics
- Spermatogenesis research
Background:
- During mammalian spermiogenesis, histones are replaced by protamines.
- Histone elimination occurs post-meiotically in spermatogenesis.
- Novel polyadenylated histone transcripts have been detected in mouse round spermatids.
Purpose of the Study:
- To investigate the characteristics of histone transcript polyadenylation in mouse round spermatids.
- To analyze the 3'-end formation of histone transcripts in spermatids.
- To determine the translatability of polyadenylated and non-polyadenylated histone transcripts.
Main Methods:
- Sequence analysis of a spermatid-specific H2a cDNA clone.
- Analysis of mature poly(A)+ mRNA transcripts in round spermatids.
- Detection of poly(A)- and poly(A)+ mRNAs on polyribosomes.
Main Results:
- A spermatid-specific H2a cDNA clone was derived from a replication-dependent histone gene.
- Polyadenylation in round spermatids occurred downstream of a purine-rich element, without the typical AATAAA signal.
- A specific H2a gene produced both polyadenylated and non-polyadenylated transcripts, suggesting sequence-dependent regulation.
- Both poly(A)- and poly(A)+ histone mRNAs were found on polyribosomes, indicating translation occurred regardless of polyadenylation.
Conclusions:
- The 3'-end formation of histone transcripts in mammalian round spermatids is unique.
- Histone translation occurs in round spermatids, irrespective of transcript polyadenylation status.
- RNA sequence influences whether histone transcripts are polyadenylated in spermatids.