RNA 5'-triphosphatase involved in mRNA 5' capping%3B subunit of mRNA capping enzyme%2C which is a heterotetramer composed of a Cet1p homodimer and two molecules of guanylyltransferase Ceg1p%3B Cet1p also has a role in regulation of RNAPII pausing at promoter-proximal sites%3B interaction between Cet1p and Ceg1p is required for Ceg1p nuclear import%3B mammalian enzyme is single bifunctional polypeptide%3B human homolog RNGTT can complement yeast cet1 null mutant