RNA polymerase, the enzyme that transcribes the genetic code

1. RNA polymerase, the enzyme that transcribes the genetic code Human body: more than 200 cell types, all have same DNA Different cell types because differences in gene expression patterns in time and space. Central Dogma of Molecular Biology: flow of genetic information from DNA (genes) to messenger RNA to enzymatically functional proteins. RNA Polymerase (RNAP) is the enzyme responsible for the first step in gene expression -- the DNA-directed synthesis of RNA -- known as transcription.

2. During transcription: RNAP powered by the free energy released by nucleotide polymerization. RNAP moves along DNA template at speeds greater than 10 nucleotides per second. RNAP can support forces greater than ~20pN These large forces allows RNAP's to displace bound proteins, such as histones, that it encounters as it transcribes along the DNA template. Ability to convert chemical energy into motion is similar to that of other motor proteins such as myosin and kinesin. Major consideration for differential gene expression: RNAP moves along DNA -- a heteropolymer, not homopolymers such as muscles’ actin or microtubules RNAP regulated by extrinsic protein factors (lac, sigma, GreA/B, rho, etc.), but also by signals encoded within the DNA template (Ia- an arrest site in human histone genes) or RNA (trp terminator sites). This extra degree of regulation makes RNAP an exquisitely controlled protein.