InterPro domain: IPR039385

The N-Utilization Substance G (NusG) protein and its eukaryotic homologue, Spt5, are involved in transcription elongation and termination. NusG contains an NGN domain at its N terminus and Kyrpides Ouzounis and Woese (KOW) repeats at its C terminus. Spt5 forms an Spt4-Spt5 complex that is an essential RNA polymerase II elongation factor. NusG was originally discovered as an N-dependent antitermination enhancing activity in Escherichia coli, and has a variety of functions such as its involvement in RNA polymerase elongation and Rho-termination in bacteria. Orthologues of the NusG gene exist in all bacteria, but their functions and requirements are different. Spt5-like is homologous to the Spt5 proteins present in all eukaryotes, which is unique as it encodes a protein with an additional long carboxy-terminal extension that contains WG/GW motifs. Spt5-like, or KTF1 (KOW domain-containing Transcription Factor 1), is a RNA-directed DNA methylation (RdDM) pathway effector in plants [ 1 , 2 ].

1. Transcription elongation: the 'Foggy' is liftingellipsis. Curr. Biol. 11, R144-6
2. Novel domains and orthologues of eukaryotic transcription elongation factors. Nucleic Acids Res. 30, 3643-52