Caught up on a fluoroquinolone technicality

[Phloston]

---

Members don't see this ad.

Are fluoroquinolones, like ciprofloxacin, in terms of the USMLE, S-phase- or G2-phase-specific, considering they're topoisomerase-II (DNA gyrase) inhibitors? I am aware that they halt G2-M progression, but that doesn't answer the question.

Thanks so much,

 

[lemonade90]

"Ciprofloxacin and other quinolones at >20 μg/ml inhibit peripheral blood lymphocyte (PBL) cell growth by 30 to 35%, causing impaired cell cycle progression through the S phase (8). "

http://aac.asm.org/content/42/8/1923.full

Makes sense as they are involved in DNA synthesis. DNA synthesis is probably impaired not allow the cell to progress passed the G2M checkpoint.

 

[Phloston]

The confusion is based on the topoisomerase activity being involved in the unwinding of the DNA, and I feel as though I can recall having heard that this occurs in early-G2, following replication in S, although I'm not entirely sure.

 

[Dr McSexy]

The confusion is based on the topoisomerase activity being involved in the unwinding of the DNA, and I feel as though I can recall having heard that this occurs in early-G2, following replication in S, although I'm not entirely sure.

Well considering you need to have unwinding and therefore subsequent relaxation in both DNA replication (during, I might add) and in transcription, I would think you would see activity in both S and G2 phases ultimately leading to enough DNA damage not to pass the G2-M checkpoint. Naturally, there's going to be a tendency to associate the affects of it it more with DNA replication. And if I had to choose one, I would say S-phase.

However, I've never seen a question asking the specifics of which cell cycle abx drugs work in, outside of the common chemotherapeutics anyway.