Characterization of the ETnII-α endogenous retroviral element in the BALB/cJ Zhx2 Afr1 allele
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Integration of mouse endogenous retroviral (MERV) elements is responsible for an estimated 10% of spontaneous mutations that have been characterized in the laboratory mouse. We recently identified a MERV integration in the first intron of the Zinc fingers and homeoboxes 2 (Zhx2) gene in BALB/cJ mice, resulting in reduced Zhx2 expression. This integration is found in BALB/cJ but not in other BALB/c substrains, indicating that it occurred after these substrains separated in the late 1930s. We have characterized this MERV element and show here that it belongs to the ETnII-α class of elements. Our analysis reveals that the Zhx2 ETn element lacks a 69-bp sequence compared to most other ETn elements which may be due to recombination between two identical 13-bp elements. Three mature Zhx2 transcripts are found in the liver of BALB/cJ mice. The major transcript is spliced from Zhx2 exon 1 to the 5′ ETn LTR and is polyadenylated at the 3′ LTR. Of the two less abundant transcripts, one is identical to the wild-type transcript, whereas the second contains 183 bp of ETn sequence spliced between Zhx2 exons 1 and 2. We have also sequenced and analyzed products from the fas lpr ETn found in MRL/lpr mice and show that it belongs to the ETnII-β class of elements.
KeywordsLong Terminal Repeat Splice Acceptor Site Chimeric Transcript Mouse Genome Database Long Terminal Repeat Element
This work was supported by the Public Health Service Grant DK59866 from the National Institute of Diabetes and Digestive and Kidney Diseases.