Binding of a phosphoprotein to the 3' untranslated region of the mouse protamine 2 mRNA temporally represses its translation.
The synthesis of the protamines, the predominant nuclear proteins of mammalian spermatozoa, is regulated during germ cell development by mRNA storage for about 7 days in the cytoplasm of differentiating spermatids. Two highly conserved sequences, the Y and H elements present in the 3' untranslated regions (UTRs) of all known mammalian protamine mRNAs, form RNA-protein complexes and specifically bind a protein of 18 kDa. Here, we show that translation of fusion mRNAs was markedly repressed in reticulocyte lysates supplemented with a mouse testis extract enriched for the 18-kDa protein when the mRNAs contained the 3' UTR of mouse protamine 2 (mP2) or the Y and H elements of mP2. No significant decrease was seen when the fusion mRNAs contained the 3' UTR of human growth hormone. The 18-kDa protein is developmentally regulated in male germ cells, requires phosphorylation for RNA binding, and is found in the ribonucleoprotein particle fractions of a testicular postmitochondrial supernatant. We propose that a phosphorylated 18-kDa protein plays a primary role in repressing translation of mP2 mRNA by interaction with the highly conserved Y and H elements. At a later stage of male gamete differentiation, the 18-kDa protein no longer binds to the mRNA, likely as a result of dephosphorylation, enabling the protamine mRNA to be translated.
Kwon
Y K
YK
Department of Biology, Tufts University, Medford, Massachusetts 02155.
Hecht
N B
NB
D000818:Animals; D001483:Base Sequence; D002474:Cell-Free System; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA; D006801:Humans; D007438:Introns; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism*; D011479:Protamines / Q000235:genetics*; D011485:Protein Binding; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism; D013087:Spermatids / Q000378:metabolism; D013737:Testis / Q000378:metabolism
D010750:Phosphoproteins; D011479:Protamines; D012333:RNA, Messenger; D012261:Ribonucleoproteins; C068621:protamine 2; D004247:DNA