RagA is a functional homologue of S. cerevisiae Gtr1p involved in the Ran/Gsp1-GTPase pathway

E Hirose, N Nakashima, T Sekiguchi… - Journal of cell …, 1998 - journals.biologists.com
E Hirose, N Nakashima, T Sekiguchi, T Nishimoto
Journal of cell science, 1998journals.biologists.com
ABSTRACT Human RagA and RagB is reported to be 52% identical to a putative GTPase of
Saccharomyces cerevisiae, Gtr1p. According to the reported nucleotide sequence, we
amplified human RagA and RagB s cDNAs from the human B cell cDNA library with PCR.
Both cDNAs rescued a cold sensitivity of S. cerevisiae, gtr1-11. Furthermore, we introduced
into the cloned human RagA cDNA, the mutation 'T21L'corresponding to the gtr1-11
mutation which has been reported to suppress not only all of rcc1−, temperature-sensitive …
Abstract
Human RagA and RagB is reported to be 52% identical to a putative GTPase of Saccharomyces cerevisiae, Gtr1p. According to the reported nucleotide sequence, we amplified human RagA and RagBs cDNAs from the human B cell cDNA library with PCR. Both cDNAs rescued a cold sensitivity of S. cerevisiae, gtr1-11. Furthermore, we introduced into the cloned human RagA cDNA, the mutation ‘T21L’ corresponding to the gtr1-11 mutation which has been reported to suppress not only all of rcc1, temperature-sensitive mutants of Ran/Gsp1p GTPase GDP/GTP-exchanging factor, but also rna1-1, a temperature-sensitive mutant of Ran/Gsp1p GTPase-activating protein. The resulting RagAgtr1-11 cDNA partially, but significantly, suppressed both rcc1 and rna1-1 mutations. These results indicated that RagA and RagBs are functional homologues of S. cervisiae Gtr1p. Interestingly, while wild-type human RagA and RagBs were localized within the cytoplasm, similar to S. cerevisiae Gtr1p, the mutated human RagAgtr1-11 corresponding to a dominant negative form of RagA was distributed in discrete speckles in the nucleus, being localized side by side with SC-35, a non-snRNP of the splicing complex. In contrast, a dominant positive form of RagA, Q66L was localized in the cytoplasm. Thus, RagA was suggested to shuttle between the cytoplasm and the nucleus, depending on the bound nucleotide state.
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