Increased expression of utrophin in a slow vs. a fast muscle involves posttranscriptional events.
Journal Article (Journal Article)
In addition to showing differences in the levels of contractile proteins and metabolic enzymes, fast and slow muscles also differ in their expression profile of structural and synaptic proteins. Because utrophin is a structural protein expressed at the neuromuscular junction, we hypothesize that its expression may be different between fast and slow muscles. Western blots showed that, compared with fast extensor digitorum longus (EDL) muscles, slow soleus muscles contain significantly more utrophin. Quantitative RT-PCR revealed that this difference is accompanied by a parallel increase in the expression of utrophin transcripts. Interestingly, the higher levels of utrophin and its mRNA appear to occur in extrasynaptic regions of muscle fibers as shown by immunofluorescence and in situ hybridization experiments. Furthermore, nuclear run-on assays showed that the rate of transcription of the utrophin gene was nearly identical between EDL and soleus muscles, indicating that increased mRNA stability accounts for the higher levels of utrophin in slow muscles. Direct plasmid injections of reporter gene constructs showed that cis-acting elements contained within the utrophin 3'-untranslated region (3'-UTR) confer greater stability to chimeric LacZ transcripts in soleus muscles. Finally, we observed a clear difference between EDL and soleus muscles in the abundance of RNA-binding proteins interacting with the utrophin 3'-UTR. Together, these findings highlight the contribution of posttranscriptional events in regulating the expression of utrophin in muscle.
Full Text
Duke Authors
Cited Authors
- Gramolini, AO; Bélanger, G; Thompson, JM; Chakkalakal, JV; Jasmin, BJ
Published Date
- October 1, 2001
Published In
Volume / Issue
- 281 / 4
Start / End Page
- C1300 - C1309
PubMed ID
- 11546668
International Standard Serial Number (ISSN)
- 0363-6143
Digital Object Identifier (DOI)
- 10.1152/ajpcell.2001.281.4.C1300
Language
- eng
Conference Location
- United States