sentences:  A method employing very gentle cell lysis in yeast followed by co-immunoprecipitation with an antibody to a mediator subunit (Med 17) has confirmed almost all previously reported or predicted interactions and revealed many previously unsuspected specific interactions of various proteins with mediator.A discussion of all mediator subunits is beyond the scope of this article, but details of one of the subunits is illustrative of the types of information that may be gathered for other subunits.Micro RNAs are involved in regulating the expression of many proteins.