TY  - JOUR
A1  - Otto, C.
A1  - Schmidt, S.
A1  - Kastner, C.
A1  - Denk, S.
A1  - Kettler, J.
A1  - Müller, N.
A1  - Germer, C.T.
A1  - Wolf, E.
A1  - Gallant, P.
A1  - Wiegering, A.
T1  - Targeting bromodomain-containing protein 4 (BRD4) inhibits MYC expression in colorectal cancer cells
JF  - Neoplasia
N2  - The transcriptional regulator BRD4 has been shown to be important for the expression of several oncogenes including MYC. Inhibiting of BRD4 has broad antiproliferative activity in different cancer cell types. The small molecule JQ1 blocks the interaction of BRD4 with acetylated histones leading to transcriptional modulation. Depleting BRD4 via engineered bifunctional small molecules named PROTACs (proteolysis targeting chimeras) represents the next-generation approach to JQ1-mediated BRD4 inhibition. PROTACs trigger BRD4 for proteasomale degradation by recruiting E3 ligases. The aim of this study was therefore to validate the importance of BRD4 as a relevant target in colorectal cancer (CRC) cells and to compare the efficacy of BRD4 inhibition with BRD4 degradation on downregulating MYC expression. JQ1 induced a downregulation of both MYC mRNA and MYC protein associated with an antiproliferative phenotype in CRC cells. dBET1 and MZ1 induced degradation of BRD4 followed by a reduction in MYC expression and CRC cell proliferation. In SW480 cells, where dBET1 failed, we found significantly lower levels of the E3 ligase cereblon, which is essential for dBET1-induced BRD4 degradation. To gain mechanistic insight into the unresponsiveness to dBET1, we generated dBET1-resistant LS174t cells and found a strong downregulation of cereblon protein. These findings suggest that inhibition of BRD4 by JQ1 and degradation of BRD4 by dBET1 and MZ1 are powerful tools for reducing MYC expression and CRC cell proliferation. In addition, downregulation of cereblon may be an important mechanism for developing dBET1 resistance, which can be evaded by incubating dBET1-resistant cells with JQ1 or MZ1.
KW  - Cancer
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-202451
VL  - 21
IS  - 11
ER  - 
TY  - JOUR
A1  - Trifault, Barbara
A1  - Mamontova, Victoria
A1  - Cossa, Giacomo
A1  - Ganskih, Sabina
A1  - Wei, Yuanjie
A1  - Hofstetter, Julia
A1  - Bhandare, Pranjali
A1  - Baluapuri, Apoorva
A1  - Nieto, Blanca
A1  - Solvie, Daniel
A1  - Ade, Carsten P.
A1  - Gallant, Peter
A1  - Wolf, Elmar
A1  - Larsen, Dorthe H.
A1  - Munschauer, Mathias
A1  - Burger, Kaspar
T1  - Nucleolar detention of NONO shields DNA double-strand breaks from aberrant transcripts
JF  - Nucleic Acids Research
N2  - RNA-binding proteins emerge as effectors of the DNA damage response (DDR). The multifunctional non-POU domain-containing octamer-binding protein NONO/p54\(^{nrb}\) marks nuclear paraspeckles in unperturbed cells, but also undergoes re-localization to the nucleolus upon induction of DNA double-strand breaks (DSBs). However, NONO nucleolar re-localization is poorly understood. Here we show that the topoisomerase II inhibitor etoposide stimulates the production of RNA polymerase II-dependent, DNA damage-inducible antisense intergenic non-coding RNA (asincRNA) in human cancer cells. Such transcripts originate from distinct nucleolar intergenic spacer regions and form DNA–RNA hybrids to tether NONO to the nucleolus in an RNA recognition motif 1 domain-dependent manner. NONO occupancy at protein-coding gene promoters is reduced by etoposide, which attenuates pre-mRNA synthesis, enhances NONO binding to pre-mRNA transcripts and is accompanied by nucleolar detention of a subset of such transcripts. The depletion or mutation of NONO interferes with detention and prolongs DSB signalling. Together, we describe a nucleolar DDR pathway that shields NONO and aberrant transcripts from DSBs to promote DNA repair.
KW  - genome integrity
KW  - repair and replication
KW  - NONO
KW  - DNA double-strand breaks
KW  - aberrant transcripts
Y1  - 2024
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350208
VL  - 52
IS  - 6
ER  -