Identification of a novel DNA-binding protein that interacts with the strong positive element of the human beta-myosin heavy chain gene.
AuthorAdamson, Cynthia Ruth, 1956-
Committee ChairMorkin, Eugene
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe human β-myosin heavy chain (βMHC) gene contains a strong positive element (SPE) at positions -298/-277 that is required for high-level expression in cultured fetal rat heart cells. This element was used to screen a fetal cardiac expression library and a single positive isolate was obtained (designated FβMBF). The nucleotide sequence of the 1.6 kb cDNA insert contained an open reading frame encoding a protein of 398 amino acids (44.1 kDa). Northern analysis to determine temporal expression of the FβMBF transcript showed expression in 15-, 17-, and 20-day rat placenta, but not in fetal rat heart or embryo at any of these developmental stages. Western blot detected an immunoreactive band of 44 kDa in 13-day fetal rat heart, and three immunoreactive bands in placenta. Coupled transcription/translation in rabbit reticulocyte lysate produced two proteins of 44 and 38 kDa. When cotransfected in an expression vector with a β-MHC reporter construct into fetal rat heart cell cultures, FβMBF caused a decrease in activity. The sequence of the 1.6 kb cDNA was not similar to any trans-acting factors previously identified in muscle, but is closely homologous to the NH₂-terminal region of two larger DNA-binding proteins PO-GA, a 128 kDa protein which may be involved in the regulation of the pituitary-specific pro-opiomelanocortin gene, and the 145 kDa subunit of Activator 1 (A1-p145), a DNA polymerase accessory protein. In the region of overlap, all three proteins contain helix-turn-turn helix (HTH) motifs which presumably represents the DNA-binding domain. FβMBF may represent an additional member of a newly described subgroup of eukaryotic HTH proteins that may play diverse roles in transcriptional regulation and DNA replication.
Degree ProgramPhysiological Sciences