Characterization of the mouse matrilin-4 gene: A 5 ' antiparallel overlap with the gene encoding the transcription factor RBP-L

We have isolated and characterized the gene encoding mouse matrilin-4 (Matn 4), an extracellular matrix protein present in a broad spectrum of tissues. The gene spanned 16 kb, consisted of 12 exons, and localized to chromosome 2. As in all known matrilin genes, the last intron, separating the exons c oding for the coiled-coil domain, did not follow the GT-AG rule and belonge d to the subgroup of introns having AT-AC at the ends. Matn4 contained two exons in the 5 ' UTR that could be alternatively spliced. We localized a ma jor and a minor transcription start site to two different untranslated exon s: exon Oa and exon Ob. Matn4 divergently overlapped 5 ' with the gene enco ding RBP-L (for recombining binding protein suppressor of hairless-like; Rb psuhl), a transcription factor with homology to RBP-J kappa. Exon I of Rbps uhl was located in the second intron of Matn4, whereas exon Oa, the first e xon of Matn4, was located in the second intron of Rbpsuhl. The second exons of the respective genes overlapped in an antisense orientation. We mapped the major transcription start of Rbpsuhl to a position approximately 150 nt upstream of the splice acceptor site of the first intron, leading to the s ynthesis of a truncated variant of RBP-L probably missing the amino-termina l 121 amino acid residues. We analyzed the expression of the different Matn 4 and Rbpsuhl transcripts by quantitative RT-PCR; this showed the highest e xpression for both genes in lung and brain. In situ hybridization of brain sections showed a partially overlapping expression pattern for the two gene s.