Nab3's localization to a nuclear granule in response to nutrient deprivation is determined by its essential prion-like domain.

Ribonucleoprotein (RNP) granules are higher order assemblies of RNA, RNA-binding proteins, and other proteins, that regulate the transcriptome and protect RNAs from environmental challenge. There is a diverse range of RNP granules, many cytoplasmic, which provide various levels of regulation of RNA metabolism. Here we present evidence that the yeast transcription termination factor, Nab3, is targeted to intranuclear granules in response to glucose starvation by Nab3's proline/glutamine-rich, prion-like domain (PrLD) which can assemble into amyloid in vitro.

The hnRNP-like Nab3 termination factor can employ heterologous prion-like domains in place of its own essential low complexity domain.

Many RNA-binding proteins possess domains with a biased amino acid content. A common property of these low complexity domains (LCDs) is that they assemble into an ordered amyloid form, juxtaposing RNA recognition motifs in a subcellular compartment in which RNA metabolism is focused. Yeast Nab3 is one such protein that contains RNA-binding domains and a low complexity, glutamine/proline-rich, prion-like domain that can self-assemble.

Recent advances in understanding transcription termination by RNA polymerase II.

Transcription termination is a fundamental process in which RNA polymerase ceases RNA chain extension and dissociates from the chromatin template, thereby defining the end of the transcription unit. Our understanding of the biological role and functional importance of termination by RNA polymerase II and the range of processes in which it is involved has grown significantly in recent years. A large set of nucleic acid-binding proteins and enzymes have been identified as part of the termination machinery.

Amyloid-like assembly of the low complexity domain of yeast Nab3.

Termination of transcription of short non-coding RNAs is carried out in yeast by the Nab3-Nrd1-Sen1 complex. Nab3 and Nrd1 are hnRNP-like proteins that dimerize and bind RNA with sequence specificity. We show here that an essential region of Nab3 that is predicted to be prion-like based upon its sequence bias, formed amyloid-like filaments.

A network of interdependent molecular interactions describes a higher order Nrd1-Nab3 complex involved in yeast transcription termination.

Nab3 and Nrd1 are yeast heterogeneous nuclear ribonucleoprotein (hnRNP)-like proteins that heterodimerize and bind RNA. Genetic and biochemical evidence reveals that they are integral to the termination of transcription of short non-coding RNAs by RNA polymerase II. Here we define a Nab3 mutation (nab3Δ134) that removes an essential part of the protein's C terminus but nevertheless can rescue, in trans, the phenotype resulting from a mutation in the RNA recognition motif of Nab3.

Yeast Nab3 protein contains a self-assembly domain found in human heterogeneous nuclear ribonucleoprotein-C (hnRNP-C) that is necessary for transcription termination.

Nab3 is an RNA-binding protein whose function is important for terminating transcription by RNA polymerase II. It co-assembles with Nrd1, and the resulting heterodimer of these heterogeneous nuclear ribonucleoprotein-C (hnRNP)-like proteins interacts with the nascent transcript and RNA polymerase II. Previous genetic analysis showed that a short carboxyl-terminal region of Nab3 is functionally important for termination and is located far from the Nab3 RNA recognition domain in the primary sequence.

A genetic screen for terminator function in yeast identifies a role for a new functional domain in termination factor Nab3.

The yeast IMD2 gene encodes an enzyme involved in GTP synthesis. Its expression is controlled by guanine nucleotides through a set of alternate start sites and an intervening transcriptional terminator. In the off state, transcription results in a short non-coding RNA that starts upstream of the gene.