Molecular cloning of rat calpactin I heavy-chain cDNA whose expression is induced in v-src-transformed rat culture cell lines.

A cDNA clone, termed N02, was isolated from a rat 3Y1 cDNA library using a differential screening procedure. The amount of N02 mRNA was increased in 3Y1 cells transformed with the Schmidt-Ruppin strain of Rous sarcoma virus (SR-3Y1) compared with that in 3Y1 cells. Sequence analysis revealed that N02 cDNA encodes a p36 calpactin I heavy chain. In addition, the amount of a p11 calpactin I light-chain mRNA was also increased in v-src-transformed rat culture cells. The expression of both p36 and p11 genes was also induced in several sets of transformed cells, including v-H-ras, v-mos- or SV40-transformed 3Y1 cells. As the expression of p36 and p11 genes was increased in transformed cells irrespective of the nature of oncogene products, overexpression of p36 and p11 genes might be involved in the key step of cellular transformation.