show Abstracthide AbstractWTX encodes a tumor suppressor implicated in Wilms tumor and in mesenchymal differentiation, with distinct functions in the cytoplasm, at the plasma membrane and in the nucleus. Here we report that the transcriptional corepressor TRIM28 is the major binding partner for nuclear WTX. The WTX-TRIM28 interaction supports chromatin binding by TRIM28, enhancing transcriptional silencing of some TRIM28 target sequences. In mouse ES cells, where TRIM28-mediated silencing of repetitive sequences is best characterized, Wtx knockdown similarly derepresses endogenous retroviruses and LINE elements. Overall design: We performed digital gene expression (DGE) profiling using Helicos RNA sequencing. Helicos sequencing does not involve an amplification step, hence it has less bias, especially in sequencing of repetitive elements. We sequenced RNA extracted from mouse ESCs harboring GFP, Wtx or Trim28 hairpins. The resulting sequence reads were aligned with the RefSeq database as well as Repbase, which is a database for the repetitive sequences.