The c-myc proto-oncogene regulates the expression of 15% to 20% of all genes, 
depending on the cell type, and the regulation is usually modest (1.5- to 
2.0-fold). The authors discovered that in addition to regulating mRNA abundance, 
c-Myc regulates the formation of the 7-methylguanosine cap on many mRNAs, 
including transcriptional target genes and others not transcriptionally 
activated. Because the 7-methylguanosine cap is required for effective 
translation, enhanced methyl cap formation leads to increased protein production 
from Myc-responsive genes that exceeds the transcriptional induction. Increased 
cap methylation is linked to Myc-dependent enhanced activity of 2 critical 
kinases, TFIIH and p-TEFb, which phosphorylate the RNA polymerase II 
carboxy-terminal domain (CTD). Phosphorylation of the CTD recruits RNGTT and 
RNMT, the enzymes involved in mRNA capping, to the nascent transcript. Evidence 
is accumulating that enhanced cap methylation makes a significant contribution 
to Myc-dependent gene regulation and protein production.