Mark Ptashne on the “incoherent and counterfactual world” of epigenetics

Ptashne again cuts through epic epigenetic confusion of transcription factors versus histone marks, cause versus effect.

“The Chemistry of Regulation of Genes and Other Things”:

As I have described, where the activated gene encodes the activator itself, we have memory: a self-perpetuating state of gene expression transmitted by regulatory proteins distributed to daughter cells as cells divide.

These now obvious ideas seem to be hard to accept for some. Ignoring the specificity problem and in the search for some alternative solution to the memory problem, they have created an incoherent and counterfactual world, one in which chromatin structure determines the activity of transcription factors (recruiters) rather than the other way around. Chromatin structure is usually meant to imply histone modifications, which somehow have acquired the name epigenetic modifications. The literature is replete with studies of histone modifications presented as studies of “epigenetics,”… Continue reading “Mark Ptashne on the “incoherent and counterfactual world” of epigenetics”