Note from the Editor.

The special section of review articles below is in honor of the centenary of the Genetics Society.

Growth factor induction by the adenovirus type 5 E1A 12S protein is required for immortalization of primary epithelial cells.

The 12S protein encoded by the adenovirus E1A region induces cellular DNA synthesis in and proliferation and immortalization of primary rat epithelial cells in the presence or absence of serum. It also induces the production of a growth factor(s) that stimulates epithelial cell proliferation. We have undertaken a mutational analysis of the 12S gene to determine the sequences required for these functions.

A retrovirus expressing the 12S adenoviral E1A gene product can immortalize epithelial cells from a broad range of rat tissues.

An epithelial cell-transforming virus could be of great use, both in the culture of epithelial cell lines and in the study of carcinogenesis. Since the adenoviral E1A gene has been shown to partially transform some epithelial cells from primary rat cell cultures, we constructed retrovirus vectors containing either the 12S or 13S E1A cDNA sequences to facilitate the transfer of these genes into a variety of primary cell types. The 12S E1A virus induced proliferation and immortalization of epithelial cells in rat kidney, liver, heart, pancreas, and thyroid primary cultures.

Growth factor(s) produced during infection with an adenovirus variant stimulates proliferation of nonestablished epithelial cells.

Infection of primary baby rat kidney cells with an adenovirus variant that encodes only the 12S gene of the E1A region, adenovirus type 5 (Ad5) 12S, results in the production of a growth factor that stimulates primary epithelial cells to proliferate. Increased epithelial cell DNA synthesis and proliferation is detectable between 24 and 36 hr after the addition of conditioned medium from Ad5 12S infected cells and not from cells infected with an E1A deletion mutant virus, Ad5 dl312. This mitogenic factor(s) is effective in the absence of serum and can override the inhibitory effect of serum on primary epithelial cells.