An analysis of the human and mouse CXCR5 gene introns

Both mouse and human chemokine receptor CXC motif 5 (CXCR5) genes exhibit one single intron interrupting the coding sequence. The mouse intron is 12053 nucleotides (nt) long; the human intron is 9603 nt long. Sections of the mouse intron significantly align plus/plus with sections of the human intron; the aligned segments are in the same order in mouse as in man and overall cover 13% of the mouse sequence and 17% of the human sequence. The human CXCR5 intron harbors sequences derived from retroviruses (human endogenous retroviruses). The mouse intron comprises very similar sequences. About 70% of the mouse intron sequence is 'specific' to this gene, while sequences in the rest of the intron are shared with many other genes located on different chromosomes. In the human the coverage by specific sequences is about 87%. Thus, the contribution of transposable elements is significantly higher in mouse (30%) than in man (13%). Intra-intronic plus/minus alignments exist in mouse (10 couples) and man (two couples): these may form stem and loop structures determining the secondary structure of the corresponding pre-mRNAs.