title: Analysis of type-I and type-II RUNX2 protein expression in osteoblasts.
abstract: Runt-related transcription factor-2 (RUNX2) is expressed as two isoforms (type-I and type-II) differing only in their amino terminal sequences. The amino terminus of type-I contains MRIPV instead of MASNSLFSAVTPCQQSFFW in type-II. Although type-II mRNA has been considered osteoblast specific, the RUNX2 protein isoforms expressed in osteoblasts have not yet been identified. Using antisera generated against the two different amino terminal sequences of type-I and type-II RUNX2, we show the expression of both isoforms in cells with the mature osteoblast phenotype (fetal rat calvarial cells, and ROS 17/2.8, SaOS-2 and U2OS osteosarcoma cell lines), but only type-I in partially differentiated osteoblast-like cells (the UMR-106 osteosarcoma cell line). Since UMR-106 cells express both type-I and type-II mRNAs, our results suggest that the translation of type-II mRNA is repressed in these cells. No RUNX1 and RUNX3 proteins are detected in any of the osteoblastic cells tested. The antisera we have generated will be useful for studies relating expression of RUNX2 isoforms to control of osteoblast differentiation.
authors.affiliation: Geriatric Research, Education, and Clinical Center, South Texas Veterans Health Care System, University of Texas Health Science Center at San Antonio, San Antonio, TX 78284, USA.
authors.forename: S
authors.initials: S
authors.lastname: Sudhakar
authors.forename: M S
authors.initials: MS
authors.lastname: Katz
authors.forename: N
authors.initials: N
authors.lastname: Elango
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D050659:Core Binding Factor Alpha 1 Subunit; D017931:DNA Primers; D006801:Humans; D007106:Immune Sera; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D010006:Osteoblasts / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000276:immunology / Q000378:metabolism
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D017931:DNA Primers; D007106:Immune Sera; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D014157:Transcription Factors