title: Mechanisms of translational repression of the Smcp mRNA in round spermatids.
abstract: The protamine 1 (Prm1) and sperm mitochondria-associated, cysteine-rich protein (Smcp) mRNAs exemplify a widespread pattern of mRNA-specific regulation of mRNA translation in post-meiotic spermatogenic cells, spermatids. Both mRNAs are transcribed and initially stored in free-mRNPs in early spermatids, and translated on polysomes in late spermatids. In this study, we demonstrate that the 5' and 3'-UTRs and the 3' terminus of the Smcp 3'-UTR are required for normal repression of the Smcp mRNA in transgenic mice. RNA affinity chromatography and mass spectrometry sequencing identified Y-box protein 2 (YBX2/MSY2) as the major protein that interacts with the 3' terminus of the Smcp 3'-UTR and a Y-box recognition sequence, GCCACCU, in the translation control element that is necessary for Prm1 mRNA repression. Depletion of YBX2 in Ybx2-null mice prematurely activates Prm1 and Smcp mRNA translation in early spermatids. Fluorescent in situ hybridization reveals that the Smcp intron, the Smcp mRNA, and both Smcp-Gfp transgenic mRNAs are strongly concentrated in the chromatoid body, and that theYbx2-null mutation does not eliminate the Smcp mRNA from the chromatoid body. This and previous findings suggest that the Smcp pre-mRNA is spliced and associates with YBX2 in the chromatoid body, and that repressed free-mRNPs are stored in the general cytoplasm. As YBX2 is the predominant protein in testis free-mRNPs, it likely represses many mRNAs in early spermatids. The mechanisms by which YBX2 represses the Smcp and Prm1 mRNAs are relevant to reproductive medicine because mutations in the human YBX2 gene correlate with abnormal protamine expression and male infertility.
authors.affiliation: Department of BiologyUniversity of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125-3393, USA.
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Cullinane
authors.affiliation: Department of BiologyUniversity of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125-3393, USA.
authors.forename: Tamjid A
authors.initials: TA
authors.lastname: Chowdhury
authors.affiliation: Department of BiologyUniversity of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125-3393, USA Kenneth.kleene@umb.edu.
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Kleene
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051140:Selenoproteins / Q000235:genetics* / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D013087:Spermatids / Q000166:cytology / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D020413:3' Untranslated Regions; C484386:Mcsp protein, mouse; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D051140:Selenoproteins; C116047:Ybx2 protein, mouse; C492024:Atp2c1 protein, mouse; D000252:Calcium-Transporting ATPases