Neonatal MMuLV infection accelerates development of thymic lymphomas in

E2A-PBX1 transgenic mice. (A) The survival for a cohort (n = 10) of E2A-PBX1 mice is compared with that for transgenic (n = 9) and nontransgenic (n = 10) littermates injected neonatally with MMuLV. Deaths were the result of malignant lymphoma confirmed by histologic examination. (B) DNA isolated from lymphomas was analyzed by Southern blot analysis using a probe specific for the MMuLV LTR. DNA was digested with NheI (N), which cuts in the U3 region of the proviral LTR, and EcoRI, which bisects the provirus (N+E). Using these conditions, proviral DNAs were detected as 2 bands, a common one of 2 kb containing a portion of the MMuLV genome and 5′ LTR, as well as a second band of unique size containing the 3′ LTR and flanking mouse genomic DNA. Clonal LTR integrations are indicated by arrows. En, endogenous cross-hybridizing retroviral genome. Ex, fragment of exogenous viral genomes containing 5′ LTR released by double enzyme digestion.