TIF-IC, a factor involved in both transcription initiation and elongation of RNA polymerase I.
We have characterized a transcription factor from Ehrlich ascites cells that is required for ribosomal gene transcription by RNA polymerase I (Pol I). This factor, termed TIF-IC, has a native molecular mass of 65 kDa, associates with Pol I, and is required both for the assembly of Sarkosyl-resistant initiation complexes and for the formation of the first internucleotide bonds. In addition to its function in transcription initiation, TIF-IC also plays a role in elongation of nascent RNA chains. At suboptimal levels of TIF-IC, transcripts with heterogeneous 3' ends are formed which are chased into full-length transcripts by the addition of more TIF-IC. Moreover, on a tailed template, which allows initiation in the absence of auxiliary factors, TIF-IC was found to stimulate the overall rate of transcription elongation and suppress pausing of Pol I. Thus TIF-IC appears to serve a function similar to the Pol II-specific factor TFIIF which is required for Pol II transcription initiation and elongation.
Schnapp
G
G
Institute of Cell and Tumor Biology, German Cancer Research Center, Heidelberg.
Schnapp
A
A
Rosenbauer
H
H
Grummt
I
I
D000818:Animals; D001483:Base Sequence; D002286:Carcinoma, Ehrlich Tumor; D002474:Cell-Free System; D008969:Molecular Sequence Data; D011485:Protein Binding; D012318:RNA Polymerase I / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D012996:Solutions; D015534:Trans-Activators / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic
D012335:RNA, Ribosomal; D012996:Solutions; D015534:Trans-Activators; D012318:RNA Polymerase I