LONG-RANGE MAPPING OF MIS-2, A COMMON PROVIRUS INTEGRATION SITE IDENTIFIED IN MURINE LEUKEMIA VIRUS-INDUCED THYMOMAS AND LOCATED 160 KILOBASE PAIRS DOWNSTREAM OF MYB

The nondefective Moloney murine leukemia virus (MuLV) induces clonal o r oligoclonal T-cell tumors in mice or rats. The proviruses of these n ondefective MuLVs have been shown to act as insertion mutagens most fr equently activating an adjacent cellular gene involved in cell growth control. Mutations by provirus insertions, recognized as common provir us integration sites, have been instrumental in identifying novel cell ular genes involved in tumor formation. We have searched for new commo n provirus integration sites in Moloney MuLV-induced thymomas. Using c ellular sequences flanking a provirus cloned from one of these tumors, we found one region, designated Mis-2, which was the target of provir us integration in a low (3%) percentage of these tumors. Mis-2 was map ped on mouse chromosome 10, approximately 160 kbp downstream of myb. T he Mis-2 region may contain a novel gene involved in tumor development .