Abstract
BackgroundMeiotic cells undergo two rounds of nuclear division and generate gametes. Previous studies have indicated that a number of transcription factors modulate the transcriptome in successive waves during meiosis and spore formation in fission yeast. However, the mechanisms underlying the post-transcriptional regulation in meiosis are not fully understood. The fission yeast spo5 + gene encodes a meiosis-specific RNA-binding protein, which is required for the progression of meiosis II and spore formation. However, the target RNA molecules of Spo5 are yet to be identified. Characterization of meiosis-specific RNA-binding proteins will provide insight into how post-transcriptional regulation influence gene expression during sexual differentiation.ResultsTo assess the functional significance of RNA-recognition motifs (RRMs) of Spo5, we constructed a series of new spo5 truncated mutants and previously reported spo5 missense mutants. In addition, we isolated novel spo5 missense mutants. The phenotypic characteristics of these mutants indicated that the RRMs are essential for both the localization and function of the protein. Interestingly, Spo5 is exported from the nucleus to the cytoplasm via the Rae1-dependent mRNA export pathway, but is unlikely to be involved in global mRNA export. Furthermore, cytoplasmic localization of Spo5 is important for its function, which suggests the involvement of Spo5 in post-transcriptional regulation. We identified pcr1 + mRNA as one of the critical targets of Spo5. The pcr1 + gene encodes an activating transcription factor/cAMP response element binding (ATF/CREB) transcription factor family. Among the four family members, namely Pcr1, Atf1, Atf21, and Atf31, only the mRNA encoding Pcr1 binds to Spo5.ConclusionsSpo5 is exported from the nucleus with mRNAs via the Rae1-dependent pathway. RRMs are necessary for this process and also for the function of Spo5 after the nuclear export. Spo5 appears to influence the activity of pcr1 + mRNA, and the mechanism of how Spo5 stimulates the mRNA to promote the progression of meiosis II and spore formation remains an intriguing question for future research.
Highlights
Meiotic cells undergo two rounds of nuclear division and generate gametes
Spo5 appears to be exported from the nucleus to the cytoplasm through the Rae1-dependent mRNA export pathway, but is unlikely to be involved in general mRNA export
As this region contains the RNA-recognition motifs (RRMs), we examined whether these might be responsible for the localization of Spo5
Summary
Meiotic cells undergo two rounds of nuclear division and generate gametes. Previous studies have indicated that a number of transcription factors modulate the transcriptome in successive waves during meiosis and spore formation in fission yeast. Meiosis is a specialized cell division process, which includes premeiotic DNA synthesis, DNA recombination followed by two rounds of cell division, and gametogenesis [1,2,3,4] It has been shown in the fission yeast Schizosaccharomyces pombe [5,6,7,8] and the budding yeast Saccharomyces cerevisiae [1,9,10,11,12] that a number of transcription factors were interested in elucidating any additional posttranscriptional regulation that might contribute to the dynamic changes observed in gene expression during meiosis in the fission yeast. Because Spo is likely to be involved in posttranscriptional events during meiosis, such as pre-mRNA processing, mRNA export, translation, and mRNA degradation, we analyzed this RNA-binding protein to evaluate its functions
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