Dataset Information

Sla1, a Schizosaccharomyces pombe homolog of the human La protein, induces ectopic meiosis when its C terminus is truncated.

ABSTRACT: Sla1 is a Schizosaccharomyces pombe homolog of the human La protein. La proteins are known to be RNA-binding proteins that bear conserved RNA recognition motifs (La and RRMs), but their biological functions still have not been fully resolved. In this study, we show that the S. pombe La homolog (Sla1) is involved in regulating sexual development. Sla1 truncated in the C terminus (Sla1DeltaC) induced ectopic sporulation in the ras1Delta strain and several other sporulation-deficient mutants. The C terminus contains a nuclear localization signal. While full-length Sla1 localizes in the nucleus, Sla1DeltaC is found throughout the cell, suggesting the cytoplasmic localization of Sla1DeltaC is involved in its sporulation-inducing activity. Further deletion analysis of Sla1 indicated that a small region (35 amino acids) that includes a portion of RRM2 is sufficient to induce sporulation. The La motif (RRM1) is not involved in this activity. Strikingly, Sla1DeltaC induced haploid meiosis in a heterothallic strain, similar to the pat1-114 or mei2-SATA mutation. Sla1DeltaC induced sporulation in a mei3 disruptant but not in a mei2 disruptant, indicating that Sla1DeltaC requires Mei2 to induce haploid meiosis. Deletion of the chromosomal sla1 gene lowered the temperature sensitivity of the pat1-114 mutant. Two-hybrid analysis indicated that Pat1 interacts with Sla1DeltaC but not full-length Sla1. Thus, Sla1DeltaC may block Pat1 activity. This block would remove the inhibition on Mei2, which would then drive the cell into haploid meiosis. Finally, Sla1 was degraded prior to the start of meiosis when we monitored Sla1 in cells in which meiosis was synchronously induced. The ability of truncated Sla1 to induce ectopic meiosis represents a very novel function that has hitherto not been suspected for the La family of proteins.

SUBMITTER: Tanabe K

PROVIDER: S-EPMC326650 | biostudies-literature | 2003 Dec

REPOSITORIES: biostudies-literature

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Sla1, a Schizosaccharomyces pombe homolog of the human La protein, induces ectopic meiosis when its C terminus is truncated.

Tanabe Kaori K Ito Noriko N Wakuri Tomomi T Ozoe Fumiyo F Umeda Makoto M Katayama Satoshi S Tanaka Katsunori K Matsuda Hideyuki H Kawamukai Makoto M

Eukaryotic cell 20031201 6

Sla1 is a Schizosaccharomyces pombe homolog of the human La protein. La proteins are known to be RNA-binding proteins that bear conserved RNA recognition motifs (La and RRMs), but their biological functions still have not been fully resolved. In this study, we show that the S. pombe La homolog (Sla1) is involved in regulating sexual development. Sla1 truncated in the C terminus (Sla1DeltaC) induced ectopic sporulation in the ras1Delta strain and several other sporulation-deficient mutants. The C ...[more]

PMID: 14665462

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Project description:Centromere integrity underlies an essential framework for precise chromosome segregation and epigenetic inheritance. Although centromeric DNA sequences vary among different organisms, all eukaryotic centromeres comprise a centromere-specific histone H3 variant, centromeric protein A (CENP-A), on which other centromeric proteins assemble into the kinetochore complex. This complex connects chromosomes to mitotic spindle microtubules to ensure accurate partitioning of the genome into daughter cells. Overexpression of CENP-A is associated with many cancers and is correlated with its mistargeting, forming extra-centromeric kinetochore structures. The mislocalization of CENP-A can be counteracted by proteolysis. The amino (N)-terminal domain (NTD) of CENP-A has been implicated in this regulation and shown to be dependent on the proline residues within this domain in Saccharomyces cerevisiae CENP-A, Cse4. We recently identified a proline-rich GRANT motif in the NTD of Schizosaccharomyces pombe CENP-A (SpCENP-A) that regulates the centromeric targeting of CENP-A via binding to the CENP-A chaperone Sim3. Here, we investigated whether the NTD is required to confer SpCENP-A turnover (i.e., counter stability) using various truncation mutants of SpCENP-A. We show that sequential truncation of the NTD did not improve the stability of the protein, indicating that the NTD of SpCENP-A does not drive turnover of the protein. Instead, we reproduced previous observations that heterochromatin integrity is important for SpCENP-A stability, and showed that this occurs in an NTD-independent manner. Cells bearing the null mutant of the histone H3 lysine 9 methyltransferase Clr4 (Δclr4), which have compromised constitutive heterochromatin integrity, showed reductions in the proportion of SpCENP-A in the chromatin-containing insoluble fraction of the cell extract, suggesting that heterochromatin may promote SpCENP-A chromatin incorporation. Thus, a disruption in heterochromatin may result in the delocalization of SpCENP-A from chromatin, thus exposing it to protein turnover. Taken together, we show that the NTD is not required to confer SpCENP-A protein turnover.

Dataset Information

Sla1, a Schizosaccharomyces pombe homolog of the human La protein, induces ectopic meiosis when its C terminus is truncated.

Publications

Sla1, a Schizosaccharomyces pombe homolog of the human La protein, induces ectopic meiosis when its C terminus is truncated.

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