Andrew S Belmont

Chromatin Structure, Gene expression, Nuclear Architecture

We are interested in how 10 and 30 nm chromatin fibers fold into interphase and mitotic chromosomes, how interphase chromosomes are moved and positioned within nuclei, and what this means for DNA functions such as transcription and replication. Currently, our understanding of these higher levels of chromatin organization, which we refer to as large-scale chromatin structure, is poor. We use a combination of molecular biology, cell biology, genetics, and microscopy to visualize nuclear positioning and folding dynamics of specific chromosome regions and individual gene loci and to relate this to regulation of transcription and replication.

We developed methods for tagging specific gene loci in live cells using operator repeats.  We applied these methods, first using engineered chromosome regions and more recently using CRISPR-based approaches to introduce these tags at endogenous loci.  These approaches allow us to study particular gene loci.  Surprisingly, over the years we found that different large-scale chromatin compaction states are tightly correlated with differential positioning within the nucleus.  Moreover, we observed directed, long-range interphase chromosome movements coupled to transcriptional activation.

Most recently, we have been using cycles of exploration using sequence-based genomic methods and  microscopy to probe how genome position may be related to regulation of gene expression examining particular gene loci.  Specifically, we developed TSA-seq to map genome-wide cytological distances of chromosome loci to specific nuclear compartments.

Our recent work has focused on the relationship between gene expression and nuclear genome positioning relative to nuclear speckles and other nuclear condensates that spatially correlate with nuclear speckles.