ABSTRACT
Maspin, also called proteinase inhibitor 5 (PI5) (OMIM # 154790), is a member of the serpin family of proteins. 1 There are an estimated 30 to 40 serpins, many occurring in clusters on different chromosomes. 2 '4 The maspin gene is located in a serpin cluster located in a 500-kb region of 18q21. There are 6 serpins in this cluster that are from the ovalbumin family of serpins (Ov-serpins). In addition to maspin, plasminogen activator inhibitor type 2 (PAI2), squamous cell carcinoma antigen-1 (SCCA 1 ) and - 2 (SCCA2 ), cytoplasmic antiproteinase 2 (PI8 ) and bomapin (PI 1 0 ) are also located in this cluster. From centromere to telomere the order is PI5-SCCA1 — SCCA2 —PAI2 —PI 1 0 —PI8 . 5,6 These genes contain seven or eight exons, and have similar exon/intron structures, and it is thought that these genes arose from duplication
M aspin , edited by Mary J.C. Hendrix. © 2 0 0 2 Eurekah.com
events. 3 Interestingly, while there is overlap in the tissue specific expression of some of these serpins, this overlap is not absolute. For instance, maspin is expressed in breast but not bone marrow or heart, while bomapin is expressed in bone marrow but not breast or heart, and PI8 is widely expressed, including heart. This suggests that in addition to divergent evolution of the proteins in this cluster, the regulatory regions of these genes are also likely to be different. One such difference is that it appears that the maspin 5’ promoter region is the only CG-rich promoter in this serpin cluster.
