Role Of Human ASB11 In Myogenesis

ASB11 is a new member of the human ankyrin repeat and SOCS box containing protein family (ASB).The family members have two functional domains:an N-terminal ankyrin-related sequence of variable repeats and a C-terminal SOCS box. ASB family members have been shown to function in biological processes relating to cell growth, tissue development, insulin signaling, via interaction with the ubiquitin and proteasomal degradation pathways, membrane skeletal proteins and so on.A novel mumber of the ASB family-ASB11 is successfully cloned from a human heart cDNA library. The gene encodes a protein containing six Ankyrin repeats at the N-terminus and one SOCS box at the C-terminus. ASB11 gene has seven exons separated by six introns and is mapped to human chromosome Xp22.31. The sequence alignment and evolutionary relationship among different ASB11 proteins with phylogenetic tree analysis indicate that ASB11 is one of the conserved proteins during evolution and belongs to the conserved ASB family. Northern blotting shows that the gene transcripts two different isoforms, one 2.9 kb and another 5.0 kb, which both are specially expressed in skeletal muscle and heart with defferent levels, suggesting that the gene may be associated with Myogenesis.The result of subcellular localization shows that ASB11 protein exists in the cell nucleus and cytoplasm. Both the mRNA and protein expression levels of ASB11 are up-regulated during myogenisis in C2C12 cells. mRNA and protein expression levels of Myf5, MyoD and Myogenin are decreased following the up-regulation of ASB11. Myf5, MyoD and Myogenin are bHLH transcriptional factors involved in myogenesis and key genes whose expression will determine whether mesodermal progenitor turn to myoblast. In addition, the results of immunofluorescence suggest that overexpression of ASB11 in C2C12 cells inhabit myotube formation during skeletal muscle cell differentiation. The results of luciferase assay suggest that overexpression of ASB11 in NIH3T3 cell depresse the transactivate of MCK and RTK promoter activity.Here we show the studies on ASB11 gene including the ORF cloning, multi tissues expression, the subcellular location, biological functions on myogenic differentiation and possible mechanisms.