Nmt. Vanderlugt et al., PROVIRAL TAGGING IN E-MU-MYC TRANSGENIC MICE LACKING THE PIM-1 PROTOONCOGENE LEADS TO COMPENSATORY ACTIVATION OF PIM-2, EMBO journal, 14(11), 1995, pp. 2536-2544
The Pim-1 proto-oncogene is one of the most potent collaborators of th
e myc proto-oncogenes in inducing lymphomagenesis in mice, Contrary to
the profound effects when overexpressed in vivo, Pim-1-deficient mice
showed only subtle phenotypic alterations, which could indicate the p
resence of redundantly acting genes, In line with this, a PCR-based sc
reen has led to the identification of a closely homologous gene, Pim-2
, The X-linked Pim-2 gene is 53% identical to Pim-1 at the amino acid
level and shares substrate preference and the usage of non-AUG initiat
ion codons with Pim-1, We have used these data to test whether the str
ong synergistic interaction between Pim-1 and c-myc can be utilized to
gain access to Pim-1 compensatory pathways. We reasoned that, upon pr
oviral tagging in compound mutant mice (E mu-myc/Pim-1(-/-) mice), the
selective advantage of cells carrying provirally activated genes, tha
t act downstream from or parallel to Pim-1, would increase. We show he
re that this is the case. A dramatic increase (from 15 to 80%) was fou
nd in the frequency of proviral activation of the Pim-2 gene, These da
ta show that the described strategy of 'complementation tagging' repre
sents a powerful new tool to identify components of pathways involved
in processes as complex as multistep tumorigenesis.