Structure and organization of the genes encoding mouse small proline-rich proteins, mSPRR1A and 1B

Two genomic clones comprising the entire coding sequence of mouse SPRR1A and 1B genes were isolated and sequenced. Sequence analysis of the 1A and 1B genomic clones indicated that both genes contain two exons separated by an intron slightly larger than 1.1kb in size (1147 and 1152nt, respectively). This type of genomic structure is identical to the counterpart of human SPRR1 gene and other genes encoding for cornified envelope proteins. Primer extension analysis using 1A and 1B gene-specific primers indicates that 1A gene is expressed in squamous tissues such as skin and esophagus, whereas 1B gene is expressed in papilloma tumors but not in squamous tissues. The first 300nt of 5'-flanking region of the mouse SPRR 1A and 1B genes reveal an overall approximately 50% identity to the human counterpart. However, there is a high degree of identity (?75%) at the promoter region containing a TATA box and TRE/TRE-like motifs. Both TATA and TRE/TRE-like motifs are almost identical in sequence and positions to those found in the counterpart of human promoter. Using transient transfection for the analysis of promoter activity, we observed that both 1A and 1B 5'-flanking regions contain the promoter activity to direct the expression of the reporter gene, chloramphenicol acetyltransferase, in airway epithelial cells in a fashion similar to that observed in the human counterpart. These results indicate a conserved nature of genetic structure and regulation of SPRR1 gene expression between human and mouse.