Mouse hepatic metallothionein-I gene cleavage by micrococcal nuclease is enhanced after induction by cadmium

Micrococcal nuclease has been shown to preferentially cleave chromatin in the region of genes actively engaged in transcription. We have used this preferential cleavage to show that the metallothionein (MT) gene in adult mouse liver, when induced to produce mRNA by injection of cadmium, becomes more susceptible to nuclease cleavage. However, the MT gene in uninduced liver, and the alphafoetal protein (AFP) gene in both induced and uninduced liver, remain relatively resistant to nuclease cleavage. The AFP gene is not normally expressed in cadmium induced or uninduced liver. Thus, susceptibility of genes to nuclease cleavage appears to rise with increasing transcription of the gene.