Question

primase is also involved in transcription. what is that? how is it done? how are promkters involved here? why must DNA be bent in us for transcription?

Answer 1

• Transcription is a process, where a DNA is copied/ transcribed to RNA.
• In DNA synthesis, primase is the starting point. Primases are enzymes, a type of RNA polymerases that synthesizes primers through short RNA sequences, which makes the primer complementary to the single stranded(ss) DNA.
• Transcription is initiated when the RNA polymerase (primase) binds to the promoter sequence. For transcription to take place, first the DNA unwinds its strands forming ss DNA. From this,RNA polymerases uses one of the ss DNA (template strand) to make complementary new RNA molecules (T nucleotides replaced with U nucleotides).

• The polymerase actually gets information from the promoter like where to start transcription in the DNA. Usually promoters consists of sequences which can be recognised by the RNA polymerases (or helper proteins ) attach to DNA. In bacteria, RNA polymerases attach directly to the promoter sequences (-10 and -35 elements) and starts transcription usually at the -10 elements which consists of many A's and T's (two hydrogen bonded, whereas C and G are three hydrogen bonded). In humans RNA polymerases binds to promoters with the aid of helper proteins.

• Bending of DNA happens when the transcription factors binds to the recognition sites present in the DNA and this could regulate transcription in many ways. Bending facilititates distantly bound transcription factors to come closer forming DNA looping or interacion between these transcription factors forms large nucleoprotein structure where DNA wraps itself around the protein complex.