Retroviral Elements and Their Hosts: Insertional Mutagenesis in the Mouse Germ Line
Figure 2
Common Effects of ETn and IAP Insertions on Gene Expression
(A) ETn effects on gene transcript processing. The most common patterns of aberrant transcript processing caused by ETns in gene introns are shown. The natural LTR polyadenylation (polyA) site and a second cryptic polyadenylation site in the internal region, along with four cryptic splice acceptors (SA) and a donor site (SD), are involved in most cases. The number of such cases is an underestimate, since several reports lack sufficient detail of aberrant transcripts. In some cases, several aberrant forms have been found. Boxes denote gene exons, thin lines denote introns, and thick lines denote spliced mRNAs, with direction of transcription from left to right. For clarity, cryptic splice acceptor sites in the 3' LTR are not shown since no documented splicing events involving these sites were found. Intronic mutagenic ETns and the affected gene are most often found in the same orientation (15 of 16 cases).
(B) IAP promoter effects on gene transcription. Ectopic gene expression driven by an antisense promoter in the 5' LTR of an IAP has been reported in eight cases. In some cases, the IAP is located a significant distance upstream of the gene.