G-quadruplexes (G4s) are prevalent DNA structures that regulate transcription but also threaten genome stability. How G4 dynamics are controlled remains poorly understood. Here, we report that RNA tra Show more
G-quadruplexes (G4s) are prevalent DNA structures that regulate transcription but also threaten genome stability. How G4 dynamics are controlled remains poorly understood. Here, we report that RNA transcripts govern G4 landscapes through coordinated G-loop assembly and disassembly. G-loop assembly involves activation of the ATM and ATR kinases, followed by homology-directed invasion of RNA opposite the G4 strand mediated by BRCA2 and RAD51. Disassembly of the G-loop resolves the G4 structure through DHX36-FANCJ-mediated G4 unwinding, which triggers nucleolytic incision and subsequent hybrid strand renewal by DNA synthesis. Inhibition of G-loop disassembly causes global G4 and R-loop accumulation, leading to transcriptome dysregulation, replication stress, and genome instability. These findings establish an intricate G-loop assembly-disassembly mechanism that controls G4 landscapes and is essential for cellular homeostasis and survival. Show less
Brain-specific neural-zinc-finger transcription factor-2b (NZF2b/7ZFMyt1) is induced in the mesolimbic dopaminergic region after chronic cocaine exposure and lentiviral-mediated expression of NZF2b/7Z Show more
Brain-specific neural-zinc-finger transcription factor-2b (NZF2b/7ZFMyt1) is induced in the mesolimbic dopaminergic region after chronic cocaine exposure and lentiviral-mediated expression of NZF2b/7ZFMyt1 in the nucleus accumbens results in decreased locomotor activity (Chandrasekar and Dreyer, 2010). In this study the role of NZF2b/7ZFMyt1 in active cocaine seeking and of its interaction with histone deacetylase on the altered behavior has been observed. Localized expression of NZF2b/7ZFMyt1 in the nucleus accumbens resulted in attenuated cocaine self-administration, whereas silencing this transcription factor with lentiviruses expressing siRNAs increased the animal's motivation to self-infuse cocaine. Low doses of sodium butyrate, a potent inhibitor of histone deacetylase, were sufficient to reverse the NZF2b/7ZFMyt1-mediated decrease in cocaine self-administration. NZF2b/7ZFMyt1 expression resulted in strong induction of transcription factors REST1 and NAC1 and of the dopamine D2 receptor, with concomitant inhibition of BDNF and its receptor TrkB. We show that NZF2b/7ZFMyt1 colocalizes with histone deacetylase-2 (HDAC2), probably overcoming the suppression of transcriptional activity caused by Lingo1. These findings show that molecular adaptations mediated by NZF2b/7ZFMyt1 expression possibly lead to decreased responsiveness to the reinforcing properties of cocaine and play a prominent role in affecting the behavioral changes induced by the drug. Show less