Project description:The HUSH complex recognizes and silences foreign DNA such as viruses, transposons, and transgenes without prior exposure to its targets. Recent studies revealed that HUSH recruitment is dependent on transcription, but a unifying molecular mechanism by which HUSH identifies its targets as ‘non-self’ DNA and selects them for silencing remains unknown. Harnessing a de novo silencing event in ESCs, we uncover distinct modes of HUSH function – one involves co-transcriptional surveillance in the absence of silencing, while the other is associated with H3K9me3 deposition and repression. We demonstrate that HUSH travels with elongating RNAPII, interacts with the transcriptional termination machinery, and accumulates on chromatin in a manner dependent on the termination factor WDR82. We further show that perturbation of endogenous termination signals triggers the switch from HUSH surveillance to silencing. Together, our results uncover an RNAi-independent, co-transcriptional gene silencing mechanism in mammals that senses aberrant termination to distinguish self from non-self.
Project description:The HUSH complex recognizes and silences foreign DNA such as viruses, transposons, and transgenes without prior exposure to its targets. Recent studies revealed that HUSH recruitment is dependent on transcription, but a unifying molecular mechanism by which HUSH identifies its targets as ‘non-self’ DNA and selects them for silencing remains unknown. Harnessing a de novo silencing event in ESCs, we uncover distinct modes of HUSH function – one involves co-transcriptional surveillance in the absence of silencing, while the other is associated with H3K9me3 deposition and repression. We demonstrate that HUSH travels with elongating RNAPII, interacts with the transcriptional termination machinery, and accumulates on chromatin in a manner dependent on the termination factor WDR82. We further show that perturbation of endogenous termination signals triggers the switch from HUSH surveillance to silencing. Together, our results uncover an RNAi-independent, co-transcriptional gene silencing mechanism in mammals that senses aberrant termination to distinguish self from non-self.
Project description:The HUSH complex recognizes and silences foreign DNA such as viruses, transposons, and transgenes without prior exposure to its targets. Recent studies revealed that HUSH recruitment is dependent on transcription, but a unifying molecular mechanism by which HUSH identifies its targets as ‘non-self’ DNA and selects them for silencing remains unknown. Harnessing a de novo silencing event in ESCs, we uncover distinct modes of HUSH function – one involves co-transcriptional surveillance in the absence of silencing, while the other is associated with H3K9me3 deposition and repression. We demonstrate that HUSH travels with elongating RNAPII, interacts with the transcriptional termination machinery, and accumulates on chromatin in a manner dependent on the termination factor WDR82. We further show that perturbation of endogenous termination signals triggers the switch from HUSH surveillance to silencing. Together, our results uncover an RNAi-independent, co-transcriptional gene silencing mechanism in mammals that senses aberrant termination to distinguish self from non-self.
Project description:The HUSH complex recognizes and silences foreign DNA such as viruses, transposons, and transgenes without prior exposure to its targets. Recent studies revealed that HUSH recruitment is dependent on transcription, but a unifying molecular mechanism by which HUSH identifies its targets as ‘non-self’ DNA and selects them for silencing remains unknown. Harnessing a de novo silencing event in ESCs, we uncover distinct modes of HUSH function – one involves co-transcriptional surveillance in the absence of silencing, while the other is associated with H3K9me3 deposition and repression. We demonstrate that HUSH travels with elongating RNAPII, interacts with the transcriptional termination machinery, and accumulates on chromatin in a manner dependent on the termination factor WDR82. We further show that perturbation of endogenous termination signals triggers the switch from HUSH surveillance to silencing. Together, our results uncover an RNAi-independent, co-transcriptional gene silencing mechanism in mammals that senses aberrant termination to distinguish self from non-self.
Project description:The HUSH complex recognizes and silences foreign DNA such as viruses, transposons, and transgenes without prior exposure to its targets. Here, we show that endogenous targets of the HUSH complex fall into two distinct classes based on the presence or absence of H3K9me3. These classes are further distinguished by their transposon content and differential response to the loss of HUSH. A de novo genomic rearrangement at the Sox2 locus induces a switch from H3K9me3-independent to H3K9me3-associated HUSH targeting, resulting in silencing. We further demonstrate that HUSH interacts with the termination factor WDR82 and-via its component MPP8-with nascent RNA. HUSH accumulates at sites of high RNAPII occupancy including long exons and transcription termination sites in a manner dependent on WDR82 and CPSF. Together, our results uncover the functional diversity of HUSH targets and show that this vertebrate-specific complex exploits evolutionarily ancient transcription termination machinery for co-transcriptional chromatin targeting and genome surveillance.