Nrd1 is a heterogeneous nuclear ribonucleoprotein (hnRNP)-like RNA-binding protein, part of the Nrd1-Nab3-Sen1 (NNS) complex which is involved in the termination and processing of short RNA polymerase II transcripts [1]. Seb1 is the Nrd1 homologue from S. pombe that is essential for cell viability and binds directly to Rpb7 subunit of RNA polymerase II. It functions in terminating all classes of Pol II-transcribed genes genome-wide. These proteins have a RNA-recognition motif (RRM, Pfam:PF00076) fused to a second alpha/beta domain described as domain 2 (also referred to as the split domain, SD, in [3]) from Nrd1 and Seb1. This domain is essential and forms a rigid body with the canonical RRM that interacts with RNA [1-3].

1: Structure and semi-sequence-specific RNA binding of Nrd1. Bacikova V, Pasulka J, Kubicek K, Stefl R; Nucleic Acids Res. 2014;42:8024-8038. PMID:24860164

2: The conserved protein Seb1 drives transcription termination by binding RNA polymerase II and nascent RNA. Wittmann S, Renner M, Watts BR, Adams O, Huseyin M, Baejen C, El Omari K, Kilchert C, Heo DH, Kecman T, Cramer P, Grimes JM, Vasiljeva L; Nat Commun. 2017;8:14861. PMID:28367989

3: The structure of transcription termination factor Nrd1 reveals an original mode for GUAA recognition. Franco-Echevarria E, Gonzalez-Polo N, Zorrilla S, Martinez-Lumbreras S, Santiveri CM, Campos-Olivas R, Sanchez M, Calvo O, Gonzalez B, Perez-Canadillas JM; Nucleic Acids Res. 2017;45:10293-10305. PMID:28973465

4: Genetic screen for suppression of transcriptional interference identifies a gain-of-function mutation in Pol2 termination factor Seb1. Schwer B, Garg A, Jacewicz A, Shuman S; Proc Natl Acad Sci U S A. 2021; [Epub ahead of print] PMID:34389684