HUMAN ENDOGENOUS RETROVIRUS EXPRESSION AND REVERSE-TRANSCRIPTASE ACTIVITY IN THE T4D MAMMARY-CARCINOMA CELL-LINE

We have examined the human mammary tumor cell line T47D and have found that these cells produce virus-like particles which band at the typic al density for retroviral particles on a sucrose gradient, possess rev erse transcriptase activity, and package HERV-K10-like sequences. Usin g this information and a bacterial expression system to identify long open reading frames, we have identified individual clones which have f ull-length open reading frames for reverse transcriptase and RNase H a nd which could encode the reverse transcriptase activity detected in t hese cells.