Active RNA polymerases: Mobile or immobile molecular machines?

It is widely assumed that active rna polymerases track along their templates to produce a transcript. we test this using chromosome conformation capture and human genes switched on rapidly and synchronously by tumour necrosis factor alpha (tnfa); one is 221 kbp samd4a,which a polymerase takes more than 1 h to transcribe. ten minutes after stimulation,the samd4a promoter comes together with other tnfa-responsive promoters. subsequently,these contacts are lost as new downstream ones appear; contacts are invariably between sequences being transcribed. super-resolution microscopy confirms that nascent transcripts (detected by rna fluorescence in situ hybridization) co-localize at relevant times. results are consistent with an alternative view of transcription: polymerases fixed in factories reel in their respective templates,so different parts of the templates transiently lie together. © 2010 papantonis et al.