A TB-RBP and Ter ATPase complex accompanies specific mRNAs from nuclei through the nuclear pores and into intercellular bridges in mouse male germ cells.
The testis brain RNA-binding protein (TB-RBP) functions as an RNA-binding protein in brain and testis, binding to conserved sequence elements present in specific mRNAs, such as protamine 1 and 2. We show here by RNA gel shift assays, immunoprecipitation, and by a novel in situ hybridization immunohistochemical technique that TB-RBP binds to AKAP4 mRNA in male mouse germ cells. AKAP4 is a component of the fibrous sheath and functions as a scaffolding protein in the sperm flagellum. AKAP4 is encoded by an X-linked gene, is expressed solely in postmeiotic (haploid) male germ cells, and is an essential protein in all spermatozoa, requiring its transport between spermatids as a protein or mRNA. AKAP4 mRNA forms a complex with TB-RBP and the Ter ATPase in nuclei and remains associated with these proteins as it exits nuclei into the cytoplasm and as it passes through intercellular bridges between spermatids. A similar mRNA-TB-RBP-Ter ATPase association is seen for protamine 2 mRNA, which is stored in the cytoplasm of postmeiotic germ cells about 7 days before translation. In contrast, no association is seen with PGK-2 mRNA which is initially transcribed early in meiosis with increased transcription in postmeiotic male germ cells. Although PGK-2 mRNA is subject to translational control, it lacks TB-RBP-binding sequences in its mRNA. The AKAP4 or protamine 2 mRNA-protein complexes dissociate in late-stage male germ cells when the mRNAs are translated. We propose that TB-RBP and the Ter ATPase are part of a complex that accompanies specific mRNAs in haploid mouse male germ cells in intracellular and intercellular movement. The temporal relationship of TB-RBP binding and mRNA inactivation in conjunction with the subsequent dissociation of the mRNA-protein complex at the time of mRNA translation suggests a role in translational suppression and/or mRNA stabilization.
Morales
Carlos R
CR
Department of Anatomy and Cell Biology, McGill University, Montreal, Canada.
Lefrancois
Stephane
S
Chennathukuzhi
Vargheese
V
El-Alfy
Mohamed
M
Wu
XinQi
X
Yang
Juxiang
J
Gerton
George L
GL
Hecht
Norman B
NB
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D017931:DNA Primers; D008297:Male; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013094:Spermatozoa / Q000378:metabolism*
D017931:DNA Primers; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000251:Adenosine Triphosphatases; C091277:TER ATPase