Localisation of metallothionein isoform mRNAs in rat hepatoma (H4) cells

The localisation of metallothionein isoform mRNAs in rat hepatoma (H4) cells was investigated using two approaches, namely Northern hybridisation of total RNA extracted from free, cytoskeletal-bound and membrane-bound polysomes isolated by a sequential detergent/salt extraction procedure and in situ hybridisation. The cytoskeletal-bound polysomes were enriched in metallothionein-I (MT-I) and c-myc mRNAs but showed a significantly lower enrichment in MT-II mRNA. These findings indicate that the MT-I mRNA is localised to the cytoskeleton during translation. In situ hybridisation using a biotin-labelled oligonucleotide probe revealed a predominantly perinuclear localisation for the MT-I mRNA.