The mouse rpL7a gene is typical of other ribosomal protein genes in it's 5' region but differs in being located in a tight cluster of CpG-rich islands.

The two major transcriptional start sites of the mouse ribosomal protein L7a gene (rpL7a) (formerly Surf-3) have been mapped to two cytidine residues separated by 4 bp embedded in a polypyrimidine tract of 21 bp. The rpL7a gene contains a small first exon (25-29 bp) and a small 5' untranslated leader sequence (22-26 bp). Its transcriptional start sites are not preceded by a canonical TATA box motif and its 5' end is located in a CpG-rich island. These are all features found associated with the five other functional mammalian ribosomal protein genes which have been previously characterized. The mouse rpL7a gene is found within a very tight cluster of six genes associated with 4 CpG-rich islands located in 32 kb of genomic DNA. Unique DNA probes located both upstream and downstream of the mouse rpL30 and rpL32 genes used on Southern blots of mouse DNA cleaved with a variety of CpG-rich island specific restriction enzymes did not detect CpG-rich islands in the close vicinity of these ribosomal protein genes. Thus the clustering of CpG-rich islands associated with rpL7a does not appear to be a general feature of mammalian ribosomal protein genes.