Purα and Purβ collaborate with Sp3 to negatively regulate β-myosin heavy chain gene expression during skeletal muscle inactivity

Juan Ji, Gretchen L. Tsika, Hansjörg Rindt, Kathy L. Schreiber, John J. McCarthy, Robert J. Kelm, Richard Tsika

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Adult skeletal muscle retains the capability of transcriptional reprogramming. This attribute is readily observable in the non-weight-bearing (NWB) soleus muscle, which undergoes a slow-to-fast fiber type transition concurrent with decreased β-myosin heavy chain (βMyHC) gene expression. Our previous work showed that Sp3 contributes to decreased βMyHC gene expression under NWB conditions. In this study, we demonstrate that physical and functional interactions between Sp3, Purα, and Purβ proteins mediate repression of βMyHC expression under NWB conditions. Binding of Purα or Purβ to the single-stranded βMyHC distal negative regulatory element-sense strand (dβNRE-S) element is markedly increased under NWB conditions. Ectopic expression of Purα and Purβ decreased βMyHC reporter gene expression, while mutation of the dβNRE-S element increased expression in C2C12 myotubes. The dβNRE-S element conferred Pur-dependent decreased expression on a minimal thymidine kinase promoter. Short interfering RNA sequences specific for Sp3 or for Purα and Purβ decreased endogenous Sp3 and Pur protein levels and increased βMyHC reporter gene expression in C2C12 myotubes. Immunoprecipitation assays revealed an association between endogenous Purα, Purβ, and Sp3, while chromatin immunoprecipitation assays demonstrated Purα, Purβ, and Sp3 binding to the βMyHC proximal promoter region harboring the dβNRE-S and C-rich elements in vivo. These data demonstrate that Pur proteins collaborate with Sp3 to regulate a transcriptional program that enables muscle cells to remodel their phenotype.

Original languageEnglish
Pages (from-to)1531-1543
Number of pages13
JournalMolecular and Cellular Biology
Issue number4
StatePublished - Feb 2007

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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