High impact information on CSE1

• Interestingly, various proteins involved in nuclear-cytoplasmic traffic, such as exportins Cse1p, Mex67p, and Los1p, exhibit a robust BA [1].
• Cse1 mediates nuclear export of importin alpha, the nuclear localization signal (NLS) import adaptor [2].
• Human CAS cDNA contains a 971-aa open reading frame that is homologous to the essential yeast gene CSE1 [3].
• Srp1p, the Saccharomyces cerevisiae homologue of importin alpha, returns from the nucleus in a complex with its export factor Cse1p and with Gsp1p (yeast Ran) in its GTP-bound state [4].
• Purified Cse1p binds with high affinity to Srp1p only in the presence of RanGTP [5].

Biological context of CSE1

• In the yeast Saccharomyces ceresivisiae, the essential gene CSE1 encodes a Cas homologue that exports the yeast importin-alpha protein Srp1p/Kap60p from the nucleus [6].
• In this report, we describe a role for the FXFG nucleoporin Nup2p, and possibly the related Nup1p, in the Cse1p-mediated nuclear export pathway [6].
• CSE1 and CSE2, two new genes required for accurate mitotic chromosome segregation in Saccharomyces cerevisiae [7].
• We cloned the CSE1 and CSE2 genes by complementation of the cold-sensitive phenotypes [7].
• Mutations in CSE1 and CSE2 have a greater effect on the segregation of chromosomes carrying mutant centromeres than on the segregation of chromosomes with wild-type centromeres [7].

Anatomical context of CSE1

• We have analyzed the effects on HeLa cells of reduction of the CAS protein, the human homologue to yeast chromosome segregation protein CSE1 [8].

Associations of CSE1 with chemical compounds

• Among them, one gene, designated as SCS2, also suppressed the choline-sensitive dominant mutation, CSE1 [Hosaka, K. et al. (1992) J. Biochem. 111, 352-358] [9].
• In CSE1, the level of inositol-1-phosphate synthase was low and was greatly repressed on the addition of choline alone [10].
• A dominant, single nuclear gene mutation, CSE1, caused inositol auxotrophy in yeast cells [10].

Physical interactions of CSE1

• After carrying its cargo into the nucleus, the importin dimer dissociates, and Srp1p (the yeast importin alpha subunit) is recycled to the cytoplasm in a complex with Cse1p and RanGTP [11].

Other interactions of CSE1

• We do not observe any biochemical interaction between Cse1p and Nup2p [6].
• Physical and genetic mapping data indicate that CSE1 is linked to HAP2 on the left arm of chromosome VII and CSE2 is adjacent to PRP2 on chromosome XIV [7].
• The CSE1 mutation is not allelic to ire15 [9].
• A dominant mutation of Saccharomyces cerevisiae, CSE1, caused a decrease in the expression of the INO1 gene product, inositol-1-phosphate synthase [12].

References