A yeast heterogeneous nuclear ribonucleoprotein complex associated with RNA polymerase II

Area of Science:

• Molecular Biology
• Gene Regulation
• Yeast Genetics

Background:

• The carboxyl-terminal domain (CTD) of RNA polymerase II (pol II) plays a role in pre-mRNA processing.
• The yeast NRD1 gene encodes an RNA-binding protein homologous to mammalian CTD-binding proteins.
• NRD1 is thought to regulate mRNA abundance via cis-acting elements.

Purpose of the Study:

• To investigate the genetic and physical interactions among Nrd1p, the pol II CTD, Nab3p, and the CTD kinase CTDK-I.
• To elucidate the role of Nrd1p and Nab3p in the context of pol II CTD function.
• To explore the involvement of these proteins in transcriptional regulation.

Main Methods:

• Yeast two-hybrid assays to detect protein-protein interactions.
• Synthetic lethality analysis using temperature-sensitive alleles and CTD truncation.
• Coimmunoprecipitation to confirm physical interactions.
• High-copy suppression studies to identify functional relationships.

Main Results:

• Nrd1p physically associates with the pol II CTD via its CTD-interaction domain.
• nrd1 temperature-sensitive alleles exhibit synthetic lethality with a truncated CTD (9-10 repeats).
• Nab3p, a hnRNP, suppresses nrd1 temperature-sensitive alleles, interacts with Nrd1p, and coimmunoprecipitates with it.
• NAB3 temperature-sensitive alleles are suppressed by deletion of CTK1, a CTD kinase.

Conclusions:

• Genetic and physical interactions suggest a collaborative role for Nrd1p, Nab3p, and CTDK-I with the pol II CTD.
• These findings indicate a significant involvement of yeast RNA-binding proteins in the regulation of transcription.
• The study highlights a complex interplay between RNA processing factors and the transcriptional machinery.