RBL2P, A YEAST PROTEIN THAT BINDS TO BETA-TUBULIN AND PARTICIPATES INMICROTUBULE FUNCTION IN-VIVO

Genetic configurations resulting in high ratios of beta-tubulin to alp ha-tubulin are toxic in S. cerevisiae, causing microtubule disassembly and cell death, We identified three non-tubulin yeast genes that, whe n overexpressed, rescue cells from excess beta-tubulin, One, RBL2, res cues beta-tubulin lethality as efficiently as does alpha-tubulin. Rbl2 p binds to beta-tubulin in vivo, Deficiencies or excesses of either Rb l2p or alpha-tubulin affect microtubule-dependent functions in a paral lel fashion, Rbl2p has functional homology with murine cofactor A, a p rotein important for in vitro assays of beta-tubulin folding. The resu lts suggest that Rbl2p participates in microtubule morphogenesis but n ot in the assembled polymer.