LC-MS/MS analysis of immunoprecipitation samples of Tetrahymena Mediator complex associated proteins

In the germline nucleus of Tetrahymena and other ciliates there occurs a peculiar burst of transcriptional activity during sexual reproduction. A major part of the genome is transcribed into noncoding RNA (ncRNA). This ncRNA serves to spot transposable elements (TEs) and other unwanted DNA sequences and marks them for elimination from the soma of the progeny. ncRNA transcription is remarkable for its extent, its occurrence in a nucleus that bears heterochromatic marks and is incapable of transcribing mRNAs and for its concomitance with meiotic DNA recombination. Here we report two novel factors (Emit1 and Emit2) that promote the micronuclear localization of the transcription Mediator complex to allow this unconventional transcriptional program to occur. Another factor (Rib1) may enhance the transcription activity to TE-rich pericentromeric and telomeric regions. The purpose of the LC-MS/MS analysis of Emit1, Emit2 and Rib1 immunoprecipitation samples is to identify their potential interacting partner proteins.