Roles of LncRNAs in Viral Infections

Liu, Weiwei; Ding, Chan

DNA methylation and histone modifications can alter the state of chromatin, resulting in transcriptional activation or silencing. In this setting, lncRNA recruits chromatin remodeling components to specific genomic loci, reprogramming the state of chromatin to silence or activate transcription ( Figure 1A) . For example, the Hox transcript antisense intergenic RNA (HOTAIR) is an lncRNA expressed from the developmental HOXC locus that can serve as a scaffold to recruit PRC2 and LSD1 in trans, leading to H3K27 methylation and H3K4me2 demethylation. (Gupta et al., 2010; Tsai et al., 2010) . H3K27 methylation is associated with transcription repression, while H3K4me2 demethylation is associated with transcription activation. Furthermore, lncRNAs can also regulate expression of neighboring genes in cis, especially in imprinting. The lncRNA Air is imprinted and expressed only from the paternal allele, which at the promoter of Slc22a3 recruits G9a and leads to targeted H3K9 methylation and allelic silencing (Nagano et al., 2008) .