Synthesis of new modified 2′,5′-adenylate trimers carrying 3′-amino-3′-deoxyadenosine at the 2′-terminus

Synthesis and Deprotection of Biodegradably and Thermally Protected Dinucleoside-2',5'-Monophosphate Prodrug Model of 2-5A

Protected dinucleoside-2',5'-monophosphate has been prepared to develop a prodrug strategy for 2-5A. The removal of enzymatically and thermally labile 4-(acetylthio)-2-(ethoxycarbonyl)-3-oxo-2-methylbutyl phosphate protecting group and enzymatically labile 3'-O-pivaloyloxymethyl group was followed at pH 7.5 and 37 °C by HPLC from the fully protected dimeric adenosine-2',5'-monophosphate 1 used as a model compound for 2-5A. The desired unprotected 2',3'-O-isopropylideneadenosine-2',5'-monophosphate (9) was observed to accumulate as a major product. Neither the competitive isomerization of 2',5'- to a 3',5'-linkage nor the P-O5' bond cleavage was detected. The phosphate protecting group was removed faster than the 3'-O-protection and, hence, the attack of the neighbouring 3'-OH on phosphotriester moiety did not take place.

The 2-5A system: modulation of viral and cellular processes through acceleration of RNA degradation

The 2-5A system is an RNA degradation pathway that can be induced by the interferons (IFNs). Treatment of cells with IFN activates genes encoding several double-stranded RNA (dsRNA)-dependent synthetases. These enzymes generate 5'-triphosphorylated, 2',5'-phosphodiester-linked oligoadenylates (2-5A) from ATP. The effects of 2-5A in cells are transient since 2-5A is unstable in cells due to the activities of phosphodiesterase and phosphatase. 2-5A activates the endoribonuclease 2-5A-dependent RNase L, causing degradation of single-stranded RNA with moderate specificity. The human 2-5A-dependent RNase is an 83.5 kDa polypeptide that has little, if any, RNase activity, unless 2-5A is present. 2-5A binding to RNase L switches the enzyme from its off-state to its on-state. At least three 2',5'-linked oligoadenylates and a single 5'-phosphoryl group are required for maximal activation of the RNase. Even though the constitutive presence of 2-5A-dependent RNase is observed in nearly all mammalian cell types, cellular amounts of 2-5A-dependent mRNA and activity can increase after IFN treatment. One well-established role of the 2-5A system is as a host defense against some types of viruses. Since virus infection of cells results in the production and secretion of IFNs, and since dsRNA is both a frequent product of virus infection and an activator of 2-5A synthesis, the replication of encephalomyocarditis virus, which produces dsRNA during its life cycle, is greatly suppressed in IFN-treated cells as a direct result of RNA decay by the activated 2-5A-dependent RNase. This review covers the organic chemistry, enzymology, and molecular biology of 2-5A and its associated enzymes. Additional possible biological roles of the 2-5A system, such as in cell growth and differentiation, human immunodeficiency virus replication, heat shock, atherosclerotic plaque, pathogenesis of Type I diabetes, and apoptosis, are presented.