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does low mRNA expression mean low relevant protein expression - looking for answers or references (May/09/2007 )

hi, dear colleagues,
my question is in the title, I am investigating mRNA expression under different culture conditions and under in vivo.
so, does low mRNA expression mean low relevent protein expression. although it sounds quite reasonable, I need much substantial explanation or reference for this question.
Thanks a lot.

-rickyama-

QUOTE (rickyama @ May 9 2007, 01:50 AM)
does low mRNA expression mean low relevent protein expression


i think so
we are doing expt on this basis

-T. reesei-

Not necessarily. Protein concentration is affected by several parameters - mainly synthesis and cleavage. So you can have situations with low mRNA expression and high levels of protein - e.g. if the protein directly influences it's expression (down-regulation of mRNA expression). But in most cases, high mRNA = high protein and low mRNA = low protein. To be sure, check both.

-kr├╝melmonster-

thanks to the above two responses.
but if one gene is down-transcription under culture, can I conclude that the corresponding protein is expressed at lower level under the culture? I think this may be much more plausible than the case of the correlation between different gene's transcription and the relevant protein's expression in cells under same condition. do you think so?

-rickyama-

Well, as mentioned above, you can assume it, but to be sure, you need to look at the protein...

-kr├╝melmonster-

yup. signaling's too complicated for you to assume a straight-across corollary. if mRNA levels go up, the potential for more protein is there...but lots of things happen between mRNA and protein, and the level could get knocked back down by other events. to prove that your treatment does, in fact, increase the amount of a protein being produced, it's very important to show at the transcriptional level and the translational, in my opinion.

-aimikins-

QUOTE (rickyama @ May 10 2007, 08:47 AM)
hi, dear colleagues,
I am investigating mRNA expression under different culture conditions and under in vivo.
so, does low mRNA expression mean low relevent protein expression. although it sounds quite reasonable, I need much substantial explanation or reference for this question.
Thanks a lot.

There is no straight correlation between mRNA expression and protein expression. Ofcourse more RNA usually leads to more protein, but also other factors are involved. Just think of regulation on the level of translation (e.g by miRs or in response to ER stress) and another very important factor is protein stability.

-Theo22-

Well, I do agree with aimikins. But I think it does make sense that low mRNA expression means low protein expression. Of course... other signalling pathway might come to affect this. Post translational modification. Translation etc.

-timjim-

not really... in the process of expression... some mRNA go through silencing process and large numbers of mRNA produce not necessary translate into large number of protein. in some cases, mRNA of certain gene was detected inlarge quantity, but while looking at protein level, there is no production of the protein coded by the mRNA. it has undergone silencing process. that happens in eukaryotic cell, but not prokaryote.

-sanjiun81-

in prokaryotes usually they do not spend energy making mRNAs if they eventually will not be translated into protein. Thats why most regulatory networks oocurs during transcription. Although in some cases, regulation occurs after that, but not as common as during transcription, and some roles also for noncoding RNAS (riboregulators)..

-arvinsign-