- In Saccharomyces cerevisiae, expression of arginine catabolic genes CAR1 and CAR2 in response to exogenous nitrogen availability is mediated by the Ume6 (CargRI)-Sin3 (CargRII)-Rpd3 (CargRIII) complex. Messenguy, F., Vierendeels, F., Scherens, B., Dubois, E. J. Bacteriol. (2000)