Analysis of the genes encoding the spp24 protein in human and mouse and identification of interacting proteins

Secreted phosphoprotein 24 (spp24) is a member of the cystatin superfamily.;This study identifies a rare single-amino acid polymorphism (p.S38F) of human spp24 and its importance has been assessed by comparing the sequence of human spp24 with that of eight other species.;The gene encoding spp24 in mouse (Spp2), like its human ortholog, comprises eight exons with an apparently TATA-les promoter. The exon-intron structure is identical in mouse and human and the size and location of intron 1 is conserved between many species. Using several strategies, the gene encoding spp24 in mouse has been mapped to 88832387-88853226 bp of the mouse chromosome 1.;An extensive expression study was carried out on the mouse and human genes encoding spp24. These studies indicated that the gene has an expression pattern of a tissue-specific and cell-specific nature, being expressed predominantly in liver and its expression is down-regulated by lipopolysaccharide (LPS) and tumour necrosis factor alpha (TNFalpha).;In an attempt to elucidate the function of the spp24 protein in mouse, a pooled-tissues cDNA library was constructed in a yeast two-hybrid vector. Two different constructs comprising the entire spp24 protein and the C-terminal non-cystatin like domain of the protein were used individually as baits in the yeast two-hybrid system to screen the constructed library. Seven potential interacting proteins were identified including granulin precursor also known as acrogranulin/epithelin (Grn), tissue specific transplantation antigen P35B (Tsta3), keratin complex 1, acidic, gene 18 (Krt1-18), keratin complex 1, acidic, gene 13 (Krtl-13 ), vimentin (Vim), similar to protein phosphatase 1, regulatory (inhibitor) subunit 12C (no gene symbol yet assigned) or myosin binding subunit 85 and alpha-actinin-4 (Actn4).