Genomic and molecular characterization of CL-43 and its proximal promoter

Collectins are part of the innate immune system as they bind nonself glycoconjugates on the surface of microorganisms and inhibit infection by direct neutralization, agglutination or opsonization of the invaders. Conglutinin and CL-43 are serum proteins that have only been found and characterized in Bovidae. We have studied molecular and genomic characteristics of CL-43 to identify polymorphisms that might be associated with disease-susceptible phenotypes or other traits in cattle, and to elucidate how the Bovidae may benefit from possessing additional collectins. Screening a bovine cDNA library resulted in the isolation of two plasmid clones that encoded the entire translated sequence of CL-43. The 5'-untranslated end and start point of transcription were identified by 5'-RACE and showed that the mRNA transcript comprises either 1326 or 1241 nucleotides because of alternative splicing. Both transcripts encode a protein of 321 amino acids including a signal peptide of 20 residues. Characterization of two overlapping genomic lambda phage clones showed that the gene comprised seven exons spanning 8.5 kbp. The CL-43 gene, like the conglutinin gene, was mapped to Bos taurus chromosome 28 at q1.8. The CL-43 promoter has 96% identity with the conglutinin promoter recently described by us, and the assignment of potential cis-regulatory elements shows that several hepatic transcription factors may regulate transcription in the acute phase response and in response to metabolic changes.