Complete cDNA cloning, genomic organization, chromosomal assignment, functional characterization of the promoter, and expression of the murine bamacan gene

Bamacan is a chondroitin sulfate proteoglycan that abounds in basement memb ranes. To gain insights into the bamacan gene regulation and transcriptiona l control, we examined the genomic organization and identified the promoter region of the mouse bamacan gene. Secondary structure analysis of the prot ein reveals a sequential organization of three globular regions interconnec ted by two cu-helix coiled-coils. The N- and the C-terminal ends carry a P- loop and a DA box motif that can act cooperatively to bind ATP, These featu res as well as the high sequence homology with members of the SMC (structur al maintenance of chromosome) protein family led us to conclude that bamaca n is a member of this protein family. The gene comprises 31 exons and is dr iven by a promoter that is highly enriched in GC sequences and lacks TATA a nd CAAT boxes. The promoter is highly functional in transient cell transfec tion assays, and step-wise 5' deletions identify a strong enhancer element between -659 and -481 base pairs that includes Jun/Fos proto-oncogene-bindi ng elements. Using backcrossing experiments we mapped the Barn gene to dist al chromosome 19, a locus syntenic to human chromosome 10q25, Bamacan is di fferentially expressed in mouse tissues with the highest levels in testes a nd brain, Notably, bamacan mRNA levels are low in normal cells and markedly reduced during quiescence but are highly increased when cells resume growt h upon serum stimulation. In contrast, in all transformed cells tested, bam acan is constitutively overexpressed, and its levels do not change with cel l cycle progression. These results suggest that bamacan is involved in the control of cell growth and transformation,