Translation initiation factor a/elF2(-γ) counteracts 5' to 3' mRNA decay in the archaeon Sulfolobus solfataricus

摘要

The trimeric translation initiation factor a/elF2 of the crenarchaeon Sulfolobus solfataricus is pivotal for binding of initiator tRNA to the ribosome. Here, we present in vitro and in vivo evidence that the a/elF2 γ-subunit exhibits an additional function with resemblance to the eukaryotic cap-complex. It binds to the 5'-triphosphate end of mRNA and protects the 5' part from degradation. This unprecedented capacity of the archaeal initiation factor further indicates that 5' → 3' directional mRNA decay is a pathway common to all domains of life.