Structural Organization and Regulation of Transcription by RNA Polymerase I of Plant Nuclear Ribosomal RNA Genes

摘要: The RNA components of the plant cytoplasmic ribosomes consist 17/18S rRNA (ribosomal RNA) in 40S ribosome subunit and 5S, 5.8S, 25S/26S 60S subunit. corresponding genes for 18S, 5.8S 25S rRNA, encoded by nuclear genome, are composed transcription units which located as rDNA DNA) repeats NOR (nucleolus organizing region) chromosome. As higher animals, 5S localized separately at other regions genome (Hemleben Grierson 1978). Coordinated regulation expression different can be expected since three polymerases involved to provide concomitantly mRNA ribosomal proteins (Sommerville 1986): polymerase I (pol I) is responsible 18S–25S transcription, III III) produces transcribed II II). question how these coordinately regulated still a fascinating problem solve eukaryotic cells. Until recently, it was believed that pots I, III, respectively, utilize completely sets initiation factors; however, has now become evident animal cells one common factor, TATA-binding protein, plays central role all (for review, see White Jackson 1992).