Polycitones, retroviral reverse

The isolation from a marine ascidian and subsequent structure determination of polycitone A (105) (Fig. 6) was first reported [52] by Kashman and coworkers in 1994. In this paper, the penta-O-methyl derivative was reported to inhibit the growth of SV40 transformed fibroblast cells at a concentration of 10 jtg/mL. Loya, Hizi and Kashman published [53] an extensive account of the biological activity of polycitone A in 1999 in which case inhibition of retroviral reverse transcriptases and cellular DNA polymerases was described. The isolation from an ascidian and structure determination of polycitone B (106) (Fig. 4) was subsequently reported [54] by Kashman and coworkers in 2000. Obviously, the presence of extensive bromination in both polycitone A and B make this family of compounds unique among the 3,4-diarylpyrrole natural products. 

Decatromicins A (1218) and B (1219) are produced by an Actinomadura sp. and are active against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (1229,1230). These compounds are closely related to pyrrolosporin A (1220) from Micromonospora sp. (1231,1232). The ascidian Polycitor africanus from Madagascar has afforded the new polycitone B (1221) (1233), which is related to the known polycitone A (1), a potent inhibitor of retroviral reverse transcriptases and cellular DNA polymerases (1234). The known polycitrin B was synthesized for the first time (1235). 

Loya S, Rudi A, Kashman Y, Hizi A (1999) Polycitone A, a Novel and Potent General Inhibitor of Retroviral Reverse Transcriptases and Cellular DNA Polymerases. Biochem J 344 85... 

Loya, S., Rudi, A., Kashman, Y., and Hizi, A. (1999) Polycitone A, a novel and potent general inhibitor of retroviral reverse transcriptases and cellular DNA polymerase. Biochem. J., 344, 85-92. 

Reverse transcriptase (RT) plays a critical role in the early steps of the life of human immunodeficiency virus (HIV) (304), and for over a decade has been one of the major targets of AIDS therapy. Polycitone A (280) was found to be a potent general inhibitor of retroviral reverse transcriptases and cellular DNA polymerases (305). Polycitone A exhibited potent inhibitory capacity of both RNA- and DNA-directed DNA polymerases. It inhibits retroviral reverse transcriptases (RTs) of human immunodeficiency virus type 1 (HIV), murine leukemia virus (MLV) and mouse mammary tumor virus (MMTV)] as efficiently as cellular DNA polymerases of both DNA polymerases a and p and the prokaryotic Klenow fragment of Escherichia coli DNA polymerase I. The mode and mechanism of inhibition of the DNA-polymerase activity associated with HIV-1 RT by polycitone A (280) have been studied. The results suggest that the inhibitory capacity of the DNA polymerase activity is independent of the template-primer used. The RNase H function is hardly affected by this inhibitor. Polycitone A has been shown to interfere with DNA primer extension, as well as with the formation of the RT-DNA complex. Steady-state kinetic studies demonstrate that this inhibitor can be considered as an allosteric inhibitor of HIV-1 RT. The target site on the enzyme may be also spatially related to the... 

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