APPARENT TRANS CONTROL OF MURINE ßGLUCURONIDASE SYNTHESIS BY A TEMPORAL GENETIC ELEMENT

Susan A. Meredith ¹ and Roger E. Ganschow ¹

¹ Institute for Developmental Research, Children's Hospital Research Foundation, Elland and Bethesda Aves., Cincinnati, Ohio 45229

A difference in the heat-inactivation kinetics between the ß-glucuronidases of C3HeB/FeJ and C57Bl/6J mice was utilized to assess the mode of action of a temporal genetic element in controlling the expression of the ß-glucuronidase structural gene Gus. The heat-inactivation kinetics of liver and kidney ß-glucuronidase from F₁ C3HeB/FeJ x C57Bl/6J animals were intermediate with respect to the parental enzyme patterns, suggesting that equal concentrations of the two allelic products were present in ß-glucuronidase tetramers of F₁ progeny. ß-glucuronidase heteropolymers assembled in vivo under conditions where equal concentrations of the two structural alleles of the enzyme were known to be present also exhibited intermediate heat-inactivation kinetics. These observations are consistent with a trans mode of action of a genetic element that controls the rate of murine ß-glucuronidase synthesis.