Transfer RNA travels from the cytoplasm to organelles.
Rubio MA, Hopper AK.
Department of Microbiology and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA.
Abstract
Transfer
RNAs (tRNAs) encoded by the nuclear genome are surprisingly dynamic.
Although tRNAs function in protein synthesis occurring on cytoplasmic
ribosomes, tRNAs can transit from the cytoplasm to the nucleus and then
again return to the cytoplasm by a process known as the tRNA retrograde
process. Subsets of the cytoplasmic tRNAs are also imported into
mitochondria and function in mitochondrial protein synthesis. The
numbers of tRNA species that are imported into mitochondria differ among
organisms, ranging from just a few to the entire set needed to decode
mitochondrially encoded mRNAs. For some tRNAs, import is dependent on
the mitochondrial protein import machinery, whereas the majority of tRNA
mitochondrial import is independent of this machinery. Although
cytoplasmic proteins and proteins located on the mitochondrial surface
participating in the tRNA import process have been described for several
organisms, the identity of these proteins differ among organisms.
Likewise, the tRNA determinants required for mitochondrial import differ
among tRNA species and organisms. Here, we present an overview and
discuss the current state of knowledge regarding the mechanisms involved
in the tRNA retrograde process and continue with an overview of tRNA
import into mitochondria. Finally, we highlight areas of future research
to understand the function and regulation of movement of tRNAs between
the cytoplasm and organelles.
