Gene structure of rat testicular cell adhesion molecule 1 (TCAM-1), and its physical linkage to genes coding for the growth hormone and BAF60b, a component of SWI/SNF complexes.

In the +9.7 to +21.7kb downstream region from the transcriptional start site of the rat growth hormone (GH) gene, a gene specifically expressed in the testis was found to have reverse transcriptional orientation to the GH gene. Its exon comprised 2693 bases encoded a protein having 548 amino acids (60479Da). The amino acid sequence of the testis-specific protein resembled that of the intercellular adhesion molecules (ICAM) 1 and 3. The gene was thus given the name testicular adhesion molecule (TCAM) 1 gene. The TCAM-1 gene was found to be 12041 bases with eight exons. Although exon 1 was noncoding, the remaining seven exons corresponded to the domains coding for the signal sequence, five immunoglobulin (Ig) domains, and the transmembrane plus cytoplasmic domain. The organization of TCAM-1 gene was shown to be the same as that of the ICAM-1 gene. The polyadenylation site of TCAM-1 gene was located 7.6kb downstream of that of the GH gene, whereas the 5' end of TCAM-1 gene was separated 5.9kb from that of the gene coding for BAF60b, a component of SWI/SNF complexes known as the chromatin remodeling factor. Six genes were thus mapped in the following order in the 88kb region of the rat GH locus: Na-channel (5' to 3')-B29/Ig-beta (5' to 3')-GH (5' to 3')-TCAM-1 (3' to 5')-BAF60b (5' to 3')-SUG/p45 (3' to 5').