Retroviral Insertions in Evi12, a Novel Common Virus Integration Site Upstream of Tra1/Grp94, Frequently Coincide with Insertions in the Gene Encoding the Peripheral Cannabinoid Receptor Cnr2

ABSTRACTThe common virus integration site (VIS) Evi11was recently identified within the gene encoding the hematopoietic G-protein-coupled peripheral cannabinoid receptor Cnr2(also referred to as Cb2). Here we show thatCnr2is a frequent target (12%) for insertion of Cas-Br-M murine leukemia virus (MuLV) in primary tumors in NIH/Swiss mice. Multiple provirus insertions in Evi11were cloned and shown to be located within the 3' untranslated region of the candidate proto-oncogene Cnr2. These results suggest that proviral insertion in the Cnr2gene is an important step in Cas-Br-M MuLV-induced leukemogenesis in NIH/Swiss mice. To isolateEvi11/Cnr2collaborating proto-oncogenes, we searched for novel common VISs in the Cas-Br-M MuLV-induced primary tumors and identified a novel frequent common VIS, Evi12(14%). Interestingly, 54% of the Evi11/Cnr2-rearranged primary tumors contained insertions in Evi12as well, which suggests cooperative action of the target genes in these two common VISs in leukemogenesis. By interspecific backcross analysis it was shown that Evi12resides on mouse chromosome 10 in a region that shares homology with human chromosomes 12q and 19p. Sequence analysis demonstrated that Evi12is located upstream of the gene encoding the molecular chaperone Tra1/Grp94, which was previously mapped to mouse chromosome 10 and human chromosome 12q22–24. Thus, Tra1/Grp94is a candidate target gene for retroviral activation or inactivation in Evi12. However, Northern and Western blot analyses did not provide evidence that proviral insertion had altered the expression ofTra1/Grp94. Additional studies are required to determine whether Tra1/Grp94or another candidate proto-oncogene inEvi12is involved in leukemogenesis.