| Budget Amount *help |
¥7,200,000 (Direct Cost: ¥7,200,000)
Fiscal Year 1997: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1996: ¥4,300,000 (Direct Cost: ¥4,300,000)
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| Research Abstract |
Nucleocytoplasmic transport of mRNA is one of the essential steps in the eukaryotic gene expression. However, a mechanism of mRNA transport is mostly unknown. To elucidate a molecular mechanism for mRNA export, we have screend a bank of mutants temperature sensitive for growth in fission yeast Schizosacccharomyces pombe by using in situ hybridization with an oligo dT probe that hybridizes to the poly A tail of mRNAs, and identified seven mutants that accumulate mRNA in the nuclei at the nonpermissive temperature. Those mutations are all recessive and fall into seven different groups designated as ptr1-7 (poly(A)^+ RNA tranport). By functional complementation using an S.pombe genomic library, we have cloned the genes complementing each mutation. Analyzes of the cloned genes revealed that ptr1^+, ptr2^+, ptr3^+, ptr4^+ and ptr6^+ encode the ubiquitin ligase E3-like protein, the guanine nucleotide exchange factor for Rna/TC4, ubiquitin activating enzyme E3, Cut1p required for the chromosome segregation, and the homologue for human TAFII55, respectively. ptr5^+ and ptr7^+ were found to encode novel proteins in S.pombe. These results suggest that the ubiquitination system plays an important role in the mRNA transport pathway, and that there might be a tight linkage between the mRNA transport and the other cellular events, such as the gene transcription and cell cycle progression
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