RTM1 - A MEMBER OF A NEW FAMILY OF TELOMERIC REPEATED GENES IN YEAST

We have isolated a new yeast gene called RTM1 whose overexpression con fers resistance to the toxicity of molasses. The RTM1 gene encodes a h ydrophobic 34-kD protein that contains seven potential transmembrane-s panning segments. Analysis of a series of industrial strains shows tha t the sequence is present in multiple copies and in variable locations in the genome. RTM loci are always physically associated with SUC tel omeric loci. The SUC-RTM sequences are located between X and Y' subtel omeric sequences at chromosome ends. Surprisingly RTM sequences are no t detected in the laboratory strain X2180. The lack of this sequence i s associated with the absence of any SUC telomeric gene previously des cribed. This observation raises the question of the origin of this non essential gene. The particular subtelomeric position might explain the SUC-RTM sequence amplification observed in the genome of yeasts used in industrial biomass or ethanol production with molasses as substrate . This SUC-RTM sequence dispersion seems to be a good example of genom ic rearrangement playing a role in evolution and environmental adaptat ion in these industrial yeasts.