Posttranslational modifications of histone N-terminal tails impact chromatin structure and gene transcription. While the extent of histone acetylation is determined by both acetyltransferases and deacetylases, it has been unclear whether histone methylation is also regulated by enzymes with opposing activities. Here, we provide evidence that LSD1 (KIAA0601), a nuclear homolog of amine oxidases, functions as a histone demethylase and transcriptional corepressor. LSD1 specifically demethylates histone H3 lysine 4, which is linked to active transcription. Lysine demethylation occurs via an oxidation reaction that generates formaldehyde. Importantly, RNAi inhibition of LSD1 causes an increase in H3 lysine 4 methylation and concomitant derepression of target genes, suggesting that LSD1 represses transcription via histone demethylation. The results thus identify a histone demethylase conserved from S. pombe to human and reveal dynamic regulation of histone methylation by both histone methylases and demethylases.

Long intergenic noncoding RNAs (lincRNAs) regulate chromatin states and epigenetic inheritance. Here we show that the lincRNA HOTAIR serves as a scaffold for at least two distinct histone modification complexes. A 5′ domain of HOTAIR binds Polycomb Repressive Complex 2 (PRC2) while a 3′ domain of HOTAIR binds the LSD1/CoREST/REST complex. The ability to tether two distinct complexes enables RNA-mediated assembly of PRC2 and LSD1, and coordinates targeting of PRC2 and LSD1 to chromatin for coupled histone H3 lysine 27 methylation and lysine 4 demethylation. Our results suggest that lincRNAs may serve as scaffolds by providing binding surfaces to assemble select histone modification enzymes, and thereby specify the pattern of histone modifications on target genes.

A newly identified coronavirus, 2019-nCoV, has been posing significant threats to public health since December 2019. ACE2, the host cell receptor for severe acute respiratory syndrome coronavirus (SARS), has recently been demonstrated in mediating 2019-nCoV infection. Interestingly, besides the respiratory system, substantial proportion of SARS and 2019-nCoV patients showed signs of various degrees of liver damage, the mechanism and implication of which have not yet been determined. Here, we performed an unbiased evaluation of cell type specific expression of ACE2 in healthy liver tissues using single cell RNA-seq data of two independent cohorts, and identified specific expression in cholangiocytes. The results indicated that virus might directly bind to ACE2 positive cholangiocytes but not necessarily hepatocytes. This finding suggested the liver abnormalities of SARS and 2019-nCoV patients may not be due to hepatocyte damage, but cholangiocyte dysfunction and other causes such as drug induced and systemic inflammatory response induced liver injury. Our findings indicate that special care of liver dysfunction should be installed in treating 2019-nCoV patients during the hospitalization and shortly after cure. : bioRxiv preprint rise of liver enzymes, implying liver function damage in patients infected with MERS-CoV [9].An very recent epidemiologic study revealed that 43 out of 99 initial patients infected with 2019-nCoV had various degrees of liver function abnormality, with alanine aminotransferase (ALT) or aspartate aminotransferase (AST) above the normal range, and more important, one