PROJECT SUMMARY/ABSTRACT
The major goal of our research program is to unravel mechanisms and detect errors during processing of
repetitive DNA or RNA sequences that could lead to genomic instability and cell dysfunction. A considerable
fraction of the genome in nearly all organisms consists of repetitive DNA sequences. It has been suggested
that these repetitive sequences play a role in several cellular processes. However, repetitive DNA sequences
can adopt non-conventional DNA and RNA structures, which can be a challenge for the DNA replication,
transcription and translation machinery to travel through and process correctly. Prolonged stalling of the
replication forks in human cells can have severe consequences, such as genome instability that include
chromosome fragility, genomic mutations and expansions of these repeat sequences. Also, repetitive
sequences located in the mRNA can interfere with translation and lead to aberrant protein expression. Several
neurological and muscular diseases are caused by repeat expansions. To avoid genomic instability at
repetitive sequences human cells employ several mechanisms to prevent genomic alterations, cell death and
diseases. BRCA1 is one of such proteins, which is involved in several molecular pathways including DNA
repair and DNA replication. However, it is not clear how much BRCA1 is needed to fulfill all BRCA1 functions
properly, and which back-up mechanisms are activated in cells with 50% of BRCA1 expression. In addition,
repetitive sequences in the mRNA can trigger repeat-associated non-UTG (RAN)-initiated translation leading to
the generation of abnormal polypeptides that form inclusions in human cells and cause several neurological,
ovarian and muscular disorders. However, the mechanisms leading to cell dysfunction, cell death and repeat
expansions induced by these abnormal inclusions are not clearly understood. In addition, it is not known which
trans factors and mechanisms promote repeat expansion in human cells. Aberrant inclusions could sequester
or dysregulate nuclear repair proteins causing DNA damage, cell dysfunction and apoptosis. In this MIRA
application we seek to determine these mechanisms and DNA repair pathways leading to genomic instability in
proliferating cells and large repeat expansion in non-proliferating human oocytes. The expected outcome of
this studies will be new knowledge how repetitive DNA and RNA sequences induce genomic instability and cell
dysfunction in so far rare studied human cells.