Accurate chromosome segregation during cell division requires physical attachment of two sister chromatids from DNA replication until mitosis, a process known as sister chromatid cohesion. Sister chromatid cohesion is mediated by a four-subunit cohesin complex that connects sister chromatids by encircling them as molecular rings. Ecol is an essential acetyltransferase required for the establishment of sister chromatid cohesion. Eco1 acetylates Smc3 and Mcd1 (Rad21) to establish cohesion during S phase and in response to DNA damage, respectively. Here, we show that Ecol repress transcription in a dose-dependent manner. Mutations of zinc-finger domain or acetyltransferase domain did not significantly affect the transcriptional repression activity of Ecol. We observed that histone demethylase, Lsd1 interacts with Eco1 and is required for the transcriptional repression activity of Ecol. Chromatin immunoprecipitation (ChIP) experiments show that Ecol facilitates the demethylation of lysine 4 of histone H3. Taken together, we provide the first evidence that Eco1 represses transcription by interacting with histone demethylase, LSD1 to convert chromatin to inactive state. (C) 2010 Elsevier Inc. All rights reserved.