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Peripheral regions of natural hammerhead ribozymes greatly increase their self-cleavage activity.

ABSTRACT: Natural hammerhead ribozymes are mostly found in some viroid and viroid-like RNAs and catalyze their cis cleavage during replication. Hammerheads have been manipulated to act in trans and assumed to have a similar catalytic behavior in this artificial context. However, we show here that two natural cis-acting hammerheads self-cleave much faster than trans-acting derivatives and other reported artificial hammerheads. Moreover, modifications of the peripheral loops 1 and 2 of one of these natural hammerheads induced a >100-fold reduction of the self-cleavage constant, whereas engineering a trans-acting artificial hammerhead into a cis derivative by introducing a loop 1 had no effect. These data show that regions external to the central conserved core of natural hammerheads play a role in catalysis, and suggest the existence of tertiary interactions between these peripheral regions. The interactions, determined by the sequence and size of loops 1 and 2 and most likely of helices I and II, must result from natural selection and should be studied in order to better understand the hammerhead requirements in vivo.

SUBMITTER: De la Pena M

PROVIDER: S-EPMC213784 | biostudies-literature | 2003 Oct

REPOSITORIES: biostudies-literature

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Peripheral regions of natural hammerhead ribozymes greatly increase their self-cleavage activity.

De la Peña Marcos M Gago Selma S Flores Ricardo R

The EMBO journal 20031001 20

Natural hammerhead ribozymes are mostly found in some viroid and viroid-like RNAs and catalyze their cis cleavage during replication. Hammerheads have been manipulated to act in trans and assumed to have a similar catalytic behavior in this artificial context. However, we show here that two natural cis-acting hammerheads self-cleave much faster than trans-acting derivatives and other reported artificial hammerheads. Moreover, modifications of the peripheral loops 1 and 2 of one of these natural ...[more]

PMID: 14532128

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Project description:BackgroundFlaxseed oil is characterized by high content of essential polyunsaturated fatty acids (PUFA) promoted as a human dietary supplement protecting against atherosclerosis. The disadvantage of the high PUFA content in flax oil is high susceptibility to oxidation, which can result in carcinogenic compound formation. Linola flax cultivar is characterized by high linoleic acid content in comparison to traditional flax cultivars rich in linolenic acid. The changes in fatty acid proportions increase oxidative stability of Linola oil and broaden its use as an edible oil for cooking. However one of investigated transgenic lines has high ALA content making it suitable as omega-3 source. Protection of PUFA oxidation is a critical factor in oil quality. The aim of this study was to investigate the impact of phenylpropanoid contents on the oil properties important during the whole technological process from seed storage to grinding and oil pressing, which may influence health benefits as well as shelf-life, and to establish guidelines for the selection of new cultivars.MethodsThe composition of oils was determined by chromatographic (GS-FID and LC-PDA-MS) methods. Antioxidant properties of secondary metabolites were analyzed by DPPH method. The stability of oils was investigated: a) during regular storage by measuring acid value peroxide value p-anisidine value malondialdehyde, conjugated dienes and trienes; b) by using accelerated rancidity tests by TBARS reaction; c) by thermoanalytical - differential scanning calorimetry (DSC).ResultsIn one approach, in order to increase oil stability, exogenous substances added are mainly lipid soluble antioxidants from the isoprenoid pathway, such as tocopherol and carotene. The other approach is based on transgenic plant generation that accumulates water soluble compounds. Increased accumulation of phenolic compounds in flax seeds was achieved by three different strategies that modify genes coding for enzymes from the phenylpropanoid pathway. The three types of transgenic flax had different phenylpropanoid profiles detected in oil, highly increasing its stability.ConclusionsWe found that hydrophilic phenylpropanoids more than lipophilic isoprenoid compounds determine oil stability however they can work synergistically. Among phenolics the caffeic acid was most effective in increasing oil stability.

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Peripheral regions of natural hammerhead ribozymes greatly increase their self-cleavage activity.

Publications

Peripheral regions of natural hammerhead ribozymes greatly increase their self-cleavage activity.

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