Premium
Translation of a unique transcript for protein isoaspartyl methyltransferase in haploid spermatids: Implications for protein storage and repair
Author(s) -
Chavous David A.,
Hake Laura E.,
Lynch Raymond J.,
O'Connor Clare M.
Publication year - 2000
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(200006)56:2<139::aid-mrd3>3.0.co;2-0
Subject(s) - biology , spermatid , spermatogenesis , messenger rna , sperm , northern blot , microbiology and biotechnology , rna , spermatocyte , western blot , andrology , gene , genetics , meiosis , endocrinology , medicine
The mammalian testis contains high levels of a protein, L‐isoaspartyl (D‐aspartyl) O ‐methyltransferase (PIMT), postulated to play a role in the repair of age‐damaged proteins. To examine the regulation of PIMT concentrations during the development of spermatozoa, poly(A)+ RNA was isolated from purified populations of pachytene spermatocytes and round spermatids. Northern blot analysis revealed that a unique 1.1–1.3 kb PIMT transcript is present in preparations of round spermatid and pachytene spermatocyte poly (A)+ RNA. The concentration of this small PIMT transcript is at least four times higher in mRNA isolated from round spermatids than in mRNA isolated from pachytene spermatocytes, indicating that the PIMT gene is actively transcribed during the haploid phase of spermatogenesis. The germ cell‐specific PIMT transcripts are distributed between the polysomal fraction and the nonpolysomal fractions of testis RNA, suggesting that translational controls also contribute to the high concentrations of PIMT in mammalian sperm. PIMT function is not essential for spermatogenesis because the testes from transgenic mice lacking PIMT activity have normal levels of protamine transcripts, and because functional sperm can be recovered from the cauda epididymis. The protein repair function of the PIMT may be more important in maintaining the fertilization competence of translationally‐inactive mature sperm during the prolonged period of epididymal transit and storage in the male reproductive tract. Mol. Reprod. Dev. 56:139–144, 2000. © 2000 Wiley‐Liss, Inc.