Understanding mRNA Polyadenylation: Key Processes and Factors

in the previous video of transcription series we discussed about the pi prime capping

process if you want to watch that video first the link is in the description

now in this video we'll be discussing about the poly administration of mrna which is also the part of mrna

processing in this polyadenylation process we get the cleavage of mrna first

at a specific sequence and then three prime end of mrnas polyadenylated before getting to the actual process

first let's see what are the requirements for polyadenylation process

first we need cpsf that's cleavage and polyadenylation specificity factors this binds to aau a signal on mrna

molecule moreover there are mainly two cpsf factors

cps of 160 and cpsf 73 and it's the cpsf 160 factor that binds aaua

signal on mrna molecule whereas the cpsf73 has hydrolysis activity and cleaves the

mrna just downstream of aaua signal which we are going to see in the later part of the

video then we have second factor that cstf cleavage stimulation factor and for the

polyadenylation process we have three cleavage stimulation factors with cstf1 and cstf2 and cstf3

this cstr factor binds u or gu rich region on mrna molecule which is mostly few bases

downstream of aauaa signal this cstr factor stimulates cps effector to drive the cleavage process

then we have the third important enzyme needed for polyadenylation process which is the polya polymerase enzyme or you

can say polyadenylate polymerase poly a polymerase catalyze the incorporation of adenine residues into

the three prime end of mrna molecule thus making polyatl of mrna

this enzyme uses single stranded rna molecule as a primer during poly retailing

furthermore we need pabp enzyme poly a binding protein this protein stimulates the activity of

poly a polymerase enzyme and also we need xrn2 which is the exo-ribonuclease it degrades left over

cleave with mrna tail and works on five prime to three prime direction on uncapped

mrna stretches now let's get to the mechanism here in this diagram we have the dna

molecule on which mrna synthesis has taken place from this mrna synthesis we get the

ammonia molecule as shown in the diagram it's having aaua signal here and u or george region here to summarize

it in a brief manner the cpsf comes in and binds aaua signal and then cstr comes in and binds you or

george region as shown in the diagram and we have the cleavage here

but let's see this process in detail by taking the mrna molecule separately we see in this animation the cps binds

the aaua region or signal and in the same way cstr binds the u or g rich region as

shown in the animation now after binding the cstf it stimulates the cpsf molecule

to drive its process and it's by the cpsc70 molecule which cleaves the mrna molecule

just downstream of aaua signal as shown in the animation now we have the three prime end without

adding in residues and to add the adenine residues here we have pap that's poly a polymerase enzyme

but it's aided by pabp once pabp binds the polymerase starts catalyzing the incorporation of adenine residues to the

three prime end of mrna thus forming the poly a tail the length of polyatl fluctuates between 50

to 250 nucleotides long so this is how the polyadenylation of mrna is done

but what polyadenylation is poor we know polyadenylation of 3n occurs just before the mrna leaves the

nucleus that means polyadenylation it is in the export of mrna molecule from nucleus to

the cytoplasm also polyadeny tail maintains the stability of

mrna molecule so this is how we get the polyadenylation of mrna molecule during the process of mrna

processing i hope you liked the video if you like it give it a thumbs up do consider

supporting my work on patreon and also make sure to subscribe this channel thanks