RIBOZYME-MEDIATED MODULATION OF HUMAN O6-METHYLGUANINE-DNA METHYLTRANSFERASE EXPRESSION

A synthetic oligonucleotide containing ribozyme sequences targeted to the 5' region of the human O6-methylguanine-DNA methyltransferase (MGM T) mRNA has been constructed. This ribozyme demonstrates cleavage acti vity in vitro in the presence of Mg2+. To determine whether this riboz yme can function in vivo, HeLa CCL2 cells were transfected with a mamm alian expression vector containing the ribozyme sequence. Following se lection and expansion of individual transfectants, a stable clone was isolated that lacks both MGMT mRNA and protein. Molecular analysis of this cell line indicates that in vivo cleavage of MGMT mRNA is respons ible for the lack of MGMT activity.