Constitutive flocculation in Saccharomyces cerevisiae through overexpression of the GTS1 gene, coding for a 'Glo'-type Zn-finger-containing protein.

The product of the cloned GTS1 gene is characterized by structural features found in transcription factors. It contains one Zn-finger motif (CXXCX16CXXC) situated in the N-terminal end with a high degree of homology to the newly identified 'Glo' family of Zn-finger proteins (Ireland et al., 1994, EMBO J. 13, 3812-3821). The C-terminal end of the protein is characterized by poly (Ala-Gln) and poly-Gln stretches. Poly-Gln are part of trans-acting motifs in known transcription factors. Overexpression of the GTS1 gene results in constitutive flocculation. Whole cell electrophoretic mobility and hydrophobicity of GTS1 overexpressing cells was respectively lower and higher relative to control cells. GTS1-induced flocculation is hardly sensitive to mannose in contrast to FLO1-determined flocculation. Overexpression of the GTS1 gene in a flo1 background does not abolish flocculation, suggesting that the FLO1 gene is not linked with the GTS1 gene in a 'flocculation pathway'.