Abstract

Spermatogenesis is a differentiation process that requires dramatic changes to DNA architecture, a process governed in part by Transition Nuclear Proteins 1 and 2 (TNP1 and TNP2). Translation of Tnp1 and Tnp2 mRNAs is temporally disengaged from their transcription. We hypothesized that RNA regulatory proteins associate specifically with Tnp mRNAs to control the delayed timing of their translation. To identify potential regulatory proteins, we isolated endogenous mRNA/protein complexes from testis extract and identified by mass spectrometry proteins that associated with one or both Tnp transcripts. Five proteins showed strong association with Tnp transcripts but had low signal when Actin mRNA was isolated. We visualized the expression patterns in testis sections of the five proteins and found that each of the proteins was detected in germ cells at the appropriate stages to regulate Tnp RNA expression.

Highlights

  • Continual sperm production throughout a male’s lifetime requires tight regulation of mitotic and meiotic divisions, shifts in gene expression and regulatory programs, dramatic morphological transformations, and unique changes to chromatin architecture

  • We cannot conclude that these are bona fide regulators of Tnp mRNAs without in vivo experiments, we found that the five proteins we identified as associated with Tnp mRNAs were expressed in the testis at appropriate times in germ cells, making them viable candidates to regulate Tnp mRNA that can be further evaluated by the field

  • The proper regulation of mRNA expression is critical to establishment and maintenance of the germline. mRNA may follow an uninterrupted process of expression, beginning with transcription and processing followed by export from the nucleus for translation

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Summary

Introduction

Continual sperm production throughout a male’s lifetime requires tight regulation of mitotic and meiotic divisions, shifts in gene expression and regulatory programs, dramatic morphological transformations, and unique changes to chromatin architecture. Basic protamines replace the standard DNA-associating histones, and Transition Nuclear Proteins (TNPs) are critical factors in the changeover. Until recently it was thought that TNPs displace histones, and protamines replace TNPs. recent data suggest an alternative mechanism by which TNPs help to condense the sperm DNA. The basic regions bind to and condense naked DNA in vitro, www.nature.com/scientificreports/. Www.nature.com/scientificreports but TNP2 has stronger affinity for DNA than TNP110. Both proteins are abundant in spermatids, but TNP1 is present at ~2-fold higher levels than TNP2 in mice. TNPs are not required for histone displacement and protamine deposition, but chromatin condensation, DNA break repair, and protamine P2 processing are defective in double knockout mice, indicating important roles for TNPs in these processes

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