The Cstf2t Polyadenylation Gene Plays a Sex-Specific Role in Learning Behaviors in Mice

Polyadenylation is an essential mechanism for the processing of mRNA 30 ends. CstF-64 (the 64,000 Mr subunit of the cleavage stimulation factor; gene symbol Cstf2) is an RNAbinding protein that regulates mRNA polyadenylation site usage. We discovered a paralogous form of CstF-64 called τCstF-64 (Cstf2t). The Cstf2t gene is conserved in all eutherian mammals including mice and humans, but the τCstF-64 protein is expressed only in a subset of mammalian tissues, mostly testis and brain. Male mice that lack Cstf2t (Cstf2t-/- mice) experience disruption of spermatogenesis and are infertile, although female fertility is unaffected. However, a role for τCstF-64 in the brain has not yet been determined. Given the importance of RNA polyadenylation and splicing in neuronal gene expression, we chose to test the hypothesis that τCstF-64 is important for brain function. Male and female 185-day old wild type and Cstf2t-/- mice were examined for motor function, general activity, learning, and memory using rotarod, open field activity, 8-arm radial arm maze, and Morris water maze tasks. Male wild type and Cstf2t-/- mice did not show differences in learning and memory. However, female Cstf2t-/- mice showed significantly better retention of learned maze tasks than did female wild type mice. These results suggest that τCstf-64 is important in memory function in female mice. Interestingly, male Cstf2t-/- mice displayed less thigmotactic behavior than did wild type mice, suggesting that Cstf2t may play a role in anxiety in males. Taken together, our studies highlight the importance of mRNA processing in cognition and behavior as well as their established functions in reproduction

The translation attenuating arginine-rich sequence in the extended signal peptide of the protein-tyrosine phosphatase PTPRJ/DEP1 is conserved in mammals.

The signal peptides, present at the N-terminus of many proteins, guide the proteins into cell membranes. In some proteins, the signal peptide is with an extended N-terminal region. Previously, it was demonstrated that the N-terminally extended signal peptide of the human PTPRJ contains a cluster of arginine residues, which attenuates translation. The analysis of the mammalian orthologous sequences revealed that this sequence is highly conserved. The PTPRJ transcripts in placentals, marsupials, and monotremes encode a stretch of 10-14 arginine residues, positioned 11-12 codons downstream of the initiating AUG. The remarkable conservation of the repeated arginine residues in the PTPRJ signal peptides points to their key role. Further, the presence of an arginine cluster in the extended signal peptides of other proteins (E3 ubiquitin-protein ligase, NOTCH3) is noted and indicates a more general importance of this cis-acting mechanism of translational suppression

TauCstF-64 Mediates Correct mRNA Polyadenylation and Splicing of Activator and Repressor Isoforms of the Cyclic AMP-Responsive Element Modulator (CREM) in Mouse Testis.

Spermatogenesis is coordinated by the spatial and temporal expression of many transcriptional and posttranscriptional factors. The cyclic AMP-responsive element modulator (CREM) gene encodes both activator and repressor isoforms that act as transcription factors to regulate spermiogenesis. We found that the testis-expressed paralog of CstF-64, tauCstF-64 (gene symbol Cstf2t), is involved in a polyadenylation site choice switch of Crem mRNA and leads to an overall decrease of the Crem mRNAs that are generated from internal promoters in Cstf2t(-/-) mice. More surprisingly, loss of tauCstF-64 also leads to alternative splicing of Crem exon 4, which contains an important activation domain. Thus, testis-specific CREMtau2 isoform protein levels are reduced in Cstf2t(-/-) mice. Consequently, expression of 15 CREM-regulated genes is decreased in testes of Cstf2t(-/-) mice at 25 days postpartum. These effects might further contribute to the infertility phenotype of these animals. This demonstrates that tauCstF-64 is an important stage-specific regulator of Crem mRNA processing that modulates the spatial and temporal expression of downstream stage-specific genes necessary for the proper development of sperm in mice. Biol Reprod 2016 Feb; 94(2):34

SHQ1 is required prior to NAF1 for assembly of H/ACA small nucleolar and telomerase RNPs

Assembly of H/ACA RNPs in yeast is aided by at least two accessory factors, Naf1p and Shq1p. Although the function of Naf1p and its human ortholog NAF1 has been delineated in detail, that of Shq1p and its putative human ortholog SHQ1 remains obscure. We demonstrate that SHQ1 indeed functions in the biogenesis of human H/ACA RNPs and we dissect its mechanism of action. Like NAF1, SHQ1 binds the major H/ACA core protein and pseudouridine synthase NAP57 (aka dyskerin) but precedes the assembly role of NAF1 at nascent H/ACA RNAs because the interaction of SHQ1 with NAP57 in vivo and in vitro precludes that of NAF1 and of the other H/ACA core proteins that are present at the sites of H/ACA RNA transcription. The N-terminal heat shock protein 20-like CS domain of SHQ1 is dispensable for NAP57 binding. Consistent with its role as an assembly factor, SHQ1 localizes to the nucleoplasm and is excluded from nucleoli and Cajal bodies, the sites of mature H/ACA RNPs. In an in vitro assembly system of functional H/ACA RNPs that is dependent on NAF1, excess recombinant SHQ1 interferes with assembly. Importantly, knockdown of cellular SHQ1 prevents accumulation of a newly synthesized H/ACA reporter RNA and generally reduces the levels of endogenous H/ACA RNAs including telomerase RNA. In summary, the sequential action of SHQ1 and NAF1 is required for functional assembly of H/ACA RNPs in vivo and in vitro. This step-wise process could serve as an efficient means of quality control during H/ACA RNP assembly

Pathogenic NAP57 mutations decrease ribonucleoprotein assembly in dyskeratosis congenita

X-linked dyskeratosis congenita (DC) is a rare bone marrow failure syndrome caused by mostly missense mutations in the pseudouridine synthase NAP57 (dyskerin/Cbf5). As part of H/ACA ribonucleoproteins (RNPs), NAP57 is important for the biogenesis of ribosomes, spliceosomal small nuclear RNPs, microRNAs and the telomerase RNP. DC mutations concentrate in the N- and C-termini of NAP57 but not in its central catalytic domain raising questions as to their impact. We demonstrate that the N- and C-termini together form the binding surface for the H/ACA RNP assembly factor SHQ1 and that DC mutations modulate the interaction between the two proteins. Pinpointing impaired interaction between NAP57 and SHQ1 as a potential molecular basis for X-linked DC has implications for therapeutic approaches, e.g. by targeting the NAP57–SHQ1 interface with small molecules