Methylation Questions - Some basic questions about methylation (Nov/01/2009 )
I am going to a talk on epigenetics and just had some basic questions about methylation.
What actually causes methylation? For example; if I went running for an hour, genes involved in energy metabolism/mitochondrial biogenesis (AMPK, PGC-1a etc) would become activated/inactivated. Would part of the modification of these genes be due to methylation?
Can all genes be methylated? If not then what does a gene need to have in order to be methylated?
I think that will do for starters. All comments are greatly appreciated.
Better read some recent nat. genet. reviews if I were you...
"What causes methylation" Dont know what you exactly mean with this question. But some sequence features have been know to be more often methylated by others. This might have to do with certain protein complexes be drawn to such sequences, such as polycomb. Furthermore there was recently shown to be an interaction between some histone modifications attracting the DNMTs and causing DNA to be methylated and vice versa also.
Most genes do not show cycling methylation; histone modifications are easier to remove and for most genes the body increases and decreases expression by modulating histone modifcations. It has however been shown that DNA methylation may be cyclic and dynamic for SOME genes. Why this is so is still big mystery, because DNA methylation removal requires the DNA repair pathway and thus costs a lot of energy in comparison to changing most (but not all) histone modifications.
In general (NOT in all cases) a gene needs to be in an active part of the nucleus, or not needed in a particular tissue, to be heavily methylated. But be aware that sometimes DNA methylation is actually required for gene activation, for instance to bind MECP2 etc. etc.
Biology...dont you just love it...every rule has an exception... keeps us from the streets and employed...
oeps a typo: active part ==> inactive part of course...