Biological JC uvssa complex alleviates myc driven transcription pressure ⼒ English

Introduce

Cancer cells develop strong genetic dependencies, enabling survival under oncogenic stress. And MYC is a key oncogene activated across most cancers. UVSSA is a gene involved in transcription-coupled repair, and its knockdown or knockout decreased cell viability when combined with MYC expression. Synthetic sick interactions between MYC expression and UVSSA down-regulation correlated with ATM/CHK2 activation, suggesting increased genome instability. The paper shows that this synthetic sick interaction is diminished by attenuating RNAPII activity, so it’s independent of UV-induced damage repair.

This means UVSSA has critical function in regulating RNAPII in the absence of exogenous DNA damage.

Figure 1

AIM

To identify proteins involved in MYC-SL/SS interactions.

RESULT

Fig.1 A:
Use community enrichment approach based on protein - protein interactions networks. After a certian steps, 18 MYC-SL/SS protein network communities were detected, coverng a variety of cellular processes.

It is obvious that the 9-th community was ranked third of average MYC-SL/SS score and was highly enriched for DNA repair proteins.

Fig.1 B:

For C and D, some analysis shows that in cancers, MYC and UVSSA may be relevant to MYC-expressing cancer cells.

Figure 2

AIM

To validate the finding and confirm that UVSSA knockdown is SL or SS with MYC activation

Fig.2 A:

Cells with UVSSA down-regulation were markedly less viable with MYC activation over the course of 30 d. It means that decreased UVSSA expression results in an SS phenotype with MYC-ER expression.

Fig.2 B:

FBCS assays showed a 67–78% decrease in the MYC ON/MYC OFF survival ratio over the course of 18 d compared with control cells, validating ERCC8 as another MYC-SS gene

Fig.2 C:

These three combinations are not significantly different from UVSSA-4 alone.
This result suggests that UVSSA and ERCC8 likely act in a complex to yield the MYC-SS effect.

Fig.1 D:

Treatment of MCF10A-MYC-ER cells with P5091, a specific small-molecule inhibitor of USP7, sensitized MYC on cells approximately threefold over MYC off cells in MTS assays.

These results support our hypothesis that down-regulating the UVSSA–USP7–ERCC8 complex is SS with MYC deregulation.

Figure 3

AIM

To find out whether the SS effect upon UVSSA down-regulation in MYC-ER cells was due to increased sensitivity to UV damage.

Fig.2 A:

Cells with UVSSA down-regulation were markedly less viable with MYC activation over the course of 30 d. It means that decreased UVSSA expression results in an SS phenotype with MYC-ER expression.

Fig.2 B:

FBCS assays showed a 67–78% decrease in the MYC ON/MYC OFF survival ratio over the course of 18 d compared with control cells, validating ERCC8 as another MYC-SS gene

Fig.2 C:

These three combinations are not significantly different from UVSSA-4 alone.
This result suggests that UVSSA and ERCC8 likely act in a complex to yield the MYC-SS effect.

Fig.1 D:

Treatment of MCF10A-MYC-ER cells with P5091, a specific small-molecule inhibitor of USP7, sensitized MYC on cells approximately threefold over MYC off cells in MTS assays.

These results support our hypothesis that down-regulating the UVSSA–USP7–ERCC8 complex is SS with MYC deregulation.