Seminar series on The Evolution of Genomic Architecture - Laura Landweber: RNA-mediated Genome Rearrangement in the Ciliate Oxytricha
- Date: Feb 28, 2019
- Time: 11:00 AM - 12:00 PM (Local Time Germany)
- Speaker: Laura Landweber from Columbia University in New York, USA
- Her you find more information on the speaker: https://biology.columbia.edu/people/landweber
- Location: MPI Plön
- Room: Lecture hall
- Host: Jenna Gallie & Julien Dutheil
Abstract:
The ciliate Oxytricha trifallax
possesses a dynamic pair of genomes, and massive DNA rearrangements
produce
a highly fragmented but functional somatic macronucleus from a complex
germline micronucleus. This process eliminates nearly all noncoding DNA,
including transposons, and rearranges over 225,000 short DNA segments
to produce a second genome containing thousands
of gene-sized "nanochromosomes." In the precursor, germline genome, the
shattered segments of different genes often interweave with each other,
frequently overlap and sometimes combinatorially assemble (Chen et al.
2014 Cell 158:1187). The mature, somatic
genome contains over 16,000 nanochromosomes (Swart et al., 2013 PLoS
Biology 11: e1001473). Noncoding RNAs regulate the entire process of
genome rearrangement. Millions of 27nt piRNAs provide the critical
information to mark and protect the retained DNA segments
of the genome (Fang et al., 2012 Cell 151:1243) and a distinct set of
piRNAs mark a subset of deleted regions to assist with their
elimination. Maternally-inherited, long, non-coding (lnc) RNAs provide
three additional layers of continuity across generations,
including serving as templates for genome remodeling and RNA-guided DNA
repair (Nowacki et al., 2008 Nature 451:153) while also regulating gene
dosage and chromosome copy number (Nowacki et al., 2010 PNAS
107:22140). This illustrates the ability of noncodingRNAs
to transmit heritable changes to the next generation. Together, Oxytricha's
elaborate epigenome, assembled through complex interacting networks of
both long and small non-coding RNAs, encapsulates an RNA-driven world,
packaged in a modern cell.