This document summarizes key aspects of transcription by the three main RNA polymerases in prokaryotes and eukaryotes. It discusses how RNA polymerase I transcribes rRNA and recognizes core and upstream promoter elements. RNA polymerase II transcription of mRNA is more complex, involving a TATA box, initiator element, and downstream element. RNA polymerase III transcribes tRNA, 5S rRNA and other small RNAs, recognizing internal type I promoters that can be split into multiple parts. The document was presented by Dr. Ujwalkumar Trivedi from the Department of Biotechnology at Marwadi University in Rajkot, Gujarat, India.

1. Presented by
Dr. Ujwalkumar Trivedi
Head
Department of Biotechnology
Marwadi University
Rajkot (Gujarat)

2.  Definition: Producing/Synthesizing RNA
molecules on DNA Template.
 RNA is single stranded
 RNA has Uracil not Thymine
 RNA can acquire secondary
structure
 RNA can have catalytic activity
 RNA is unstable at alkaline pH

3. In prokaryotes, transcription is coupled with translation in cytoplasm. In
eukaryotes, transcription and post transcriptional modification takes place
in nucleus and later the mature/processed RNA is transported out of
nucleus where the process of translation takes place.

4.  Regulation very complex
 Three different pols
 Distinguished by -amanitin sensitivity
◦ Pol I—rRNA, least sensitive
◦ Pol II– mRNA, most sensitive
◦ Pol III– tRNA and 5R RNA moderately sensitive
 Each polymerase recognizes a distinct
promoter

6.  RNA Polymerase I
◦ Transcribes rRNA
◦ Sequence not well conserved
 Two elements
◦ Core element- surrounds the transcription start site
(-45 to + 20)
◦ Upstream control element- between -156 and -107
upstream
◦ Spacing affects strength of transcription

7.  Much more complicated
 Two parts
◦ Core promoter
◦ Upstream element
 Core promoter
◦ TATA box at ~-30 bases
◦ Initiator—on the transcription start site
◦ Downstream element-further downstream
 Many natural promoters lack recognizable
versions of one or more of these sequences

14.  Precursors to tRNAs,5SrRNA, other small
RNAs
 Promoter Type I
◦ Lies completely within the transcribed region
◦ 5SrRNA promoter split into 3 parts
◦ tRNA promoters split into two parts
 Polymerase II-like promoters
◦ EX. snRNA
◦ Lack internal promoter
◦ Resembles pol II promoter in both sequence and
position

17. Thank You
Kindly Reach us at:
Marwadi University
Rajkot-Morbi Highway Road, Gauridad, Rajkot, Gujarat 360003
Website: https://www.marwadieducation.edu.in/