Julien Mozziconacci

ALT Chromatin plays a pivotal role in genome expression, maintenance, and replication. To better understand chromatin organization, we developed a novel proximity-tagging method which assigns unique DNA barcodes to molecules that associate in 3D space. Using this method – Proximity Copy Paste (PCP) – we mapped the connectivity of individual nucleosomes in Saccharomyces cerevisiae. We show that chromatin is predominantly organized into regularly spaced nucleosome arrays whose properties differ according to transcriptional activity. Additionally, by mapping long-range, multi-way interactions we provide evidence that metaphase chromosomes are compacted by arrayed cohesin hubs. Using single-molecule nuclease footprinting data we define distinct chromatin states within a mixed population to show that noncanonical nucleosomes are a stable feature of chromatin. PCP is a versatile method allowing the connectivity of individual molecules to be mapped at high-resolution.

ALT Most of the human genome is thought to be non-functional, and includes large segments often referred to as "dark matter" DNA. The genome also encodes hundreds of putative and poorly characterized transcription factors (TFs). We determined genomic binding locations of 166 uncharacterized human TFs in living cells. Nearly half of them associated strongly with known regulatory regions such as promoters and enhancers, often at conserved motif matches and co-localizing with each other. Surprisingly, the other half often associated with genomic dark matter, at largely unique sites, via intrinsic sequence recognition. Dozens of these, which we term "Dark TFs", mainly bind within regions of closed chromatin. Dark TF binding sites are enriched for transposable elements, and are rarely under purifying selection. Some Dark TFs are KZNFs, which contain the repressive KRAB domain, but many are not: the Dark TFs also include known or potential pioneer TFs...