Rtp1p Is a Karyopherin-Like Protein Required for RNA Polymerase II Biogenesis

Abstract

The assembly and nuclear transport of RNA polymerase II (RNA pol II) are processes that require the participation of many auxiliary factors. In a yeast genetic screen, we identified a previously uncharacterized gene, YMR185w (renamed RTP1), which encodes a protein required for the nuclear import of RNA pol II. Using protein affinity purification coupled to mass spectrometry, we identified interactions between Rtp1p and members of the R2TP complex. Rtp1p also interacts, to a different extent, with several RNA pol II subunits. The pattern of interactions is compatible with a role for Rtp1p as an assembly factor that participates in the formation of the Rpb2/Rpb3 subassembly complex and its binding to the Rpb1p-containing subcomplex. Besides, Rtp1p has a molecular architecture characteristic of karyopherins, composed of HEAT repeats, and is able to interact with phenylalanine-glycine-containing nucleoporins. Our results define Rtp1p as a new component of the RNA pol II biogenesis machinery that plays roles in subunit assembly and likely in transport through the nuclear pore complex.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01449-12.

ACKNOWLEDGMENTS

We thank the anonymous reviewers for their valuable comments and suggestions. We also thank C. Cole, E. Herrero, J. C. Igual, E. Hurt, and M. Pamblanco for providing the plasmids and yeast strains. We appreciate the advice from J. C. Igual and I. Quilis on microscope usage.

This work was supported by grants from the Spanish Ministry of Education and Science (BFU2008-04082-C02-01/BMC and BFU2011-23501/BMC) and from the Generalitat Valenciana (Valencian Regional Government: ACOMP2011/233) to F.E. N.G.-N. is the recipient of a fellowship from the F.P.I. program Cinc Segles at the Universitat de València.