Bd. Manning et al., THE RHO-GEF ROM2P LOCALIZES TO SITES OF POLARIZED CELL-GROWTH AND PARTICIPATES IN CYTOSKELETAL FUNCTIONS IN SACCHAROMYCES-CEREVISIAE, Molecular biology of the cell, 8(10), 1997, pp. 1829-1844
Rom2p is a GDP/GTP exchange factor for Rho1p and Rho2p GTPases; Rho pr
oteins have been implicated in control of actin cytoskeletal rearrange
ments. ROM2 and RHO2 were identified in a screen for high-copy number
suppressors of cik1 Delta, a mutant defective in microtubule-based pro
cesses in Saccharomyces cerevisiae. A Rom2p::3XHA fusion protein local
izes to sites of polarized cell growth, including incipient bud sites,
tips of small buds, and tips of mating projections. Disruption of ROM
2 results in temperature-sensitive growth defects at 11 degrees C and
37 degrees C. rom2 Delta cells exhibit morphological defects. At permi
ssive temperatures, rom2 Delta cells often form elongated buds and fai
l to form normal mating projections after exposure to pheromone; at th
e restrictive temperature, small budded cells accumulate. High-copy nu
mber plasmids containing either ROM2 or RHO2 suppress the temperature-
sensitive growth defects of cik1 Delta and kar3 Delta strains. KAR3 en
codes a kinesin-related protein that interacts with Cik1p. Furthermore
, rom2 Delta strains exhibit increased sensitivity to the microtubule
depolymerizing drug benomyl. These results suggest a role for Rom2p in
both polarized morphogenesis and functions of the microtubule cytoske
leton.