Introduction
Suppose if small RNA molecule might function as an enzyme and regulate essential processes in living cells. This surprising discovery transformed the study of molecular biology and introduced scientists to ribozymes. Ribozyme technology deals with the use of ribozymes for different purposes including therapeutic and research purposes. RNA molecules can also act like enzymes and perform catalytic activities inside living cells.History
The first ribozyme was discovered in 1980. Researchers demonstrated that RNA functions both as a genetic material and as a biological catalyst. This contributed to the worldwide hypothesis that RNA may have played a crucial role in the evolution of self-replicating systems. This is referred to as the RNA world hypothesis. It has a special active site made completely of RNA, which helps it perform its function like an enzyme.
Catalytic Activity
Ribozymes are catalytically active RNA molecules that can cleave mRNA molecules in a sequence-specific way. They contain sequences for selective ligation with target mRNAs, which confers upon them high specificity. Ribozyme can be classified into two different groups:- The self-cleaving (30-150 nucleotide long) RNAs which include the hammerhead, hairpin, hepatitis delta virus, and satellite.
- The self-splicing ribozymes (100-3000 nucleotide long) that are the group I and group II introns, RNase P.
- Group I intron ribozymes are one of the most common types of ribozymes found in bacteria, lower eukaryotes, and higher plants. They are inserted into the genes of a wide range of bacteriophages of Gram-positive bacteria.
- Group II introns have been found in bacteria and in the mitochondrial and chloroplast genomes of fungi, plants, protists, and an annelid worm.
Mechanism
Ribozymes work by recognizing and binding to a specific RNA sequence. In this process, the 2’-OH group of a particular adenosine acts as a nucleophile and attacks the 5’ splice site, forming a branched intron structure. Then, the 3’-OH group of the 5’ exon attacks the 3’ splice site, joining the exons together and releasing the intron in the form of a lariat structure.1. Self Cleaving Ribozyme
RNase P The first functional RNA enzyme that investigators found was ribonuclease P (RNase P). It acts as an endonuclease to generate the mature 5’ end of tRNA precursors. It requires divalent cations for cleaving. The mechanism of cleavage is hydrolysis rather than transesterification. RNase P lacks the requirement for a specific nucleotide sequence for cleavage.Hammerhead Ribozyme
Hammerhead ribozymes(HHRZs) are tiny autocatalytic RNAS that cleave single stranded RNA, is so named because its secondary structure is similarly to that of a hammer head, but actually its tertiary structure is more like Y shaped. They are present in nature as a part of some virus-like structures known as virusoids, that replicate its tiny, circular RNA genomes using a rolling circle replication mechanism.
- Cis Acting Hammer Head Ribozyme
Self splicing occurs after the sequence guc between helix I and helix III, where
g and u are protected and required for catalysis. - Trans Acting Hammer Head Ribozyme
designed to cleave RNA in trans by adding a recognition sequence to the
substrate and detaching the catalytic domain from the ribozyme.Hairpin Ribozyme
2. Self splicing Ribozyme
Group I Intron
Self splicing by Trans esterification process
First transfer: 3’OH end of G attack 5’ end of intron
Second transfer: 3’OH of exon A attack 5’ end of exonB
Group II Intron
Commonly found in mitochondrial genes in plants,fungi and yeast
Do not require free guanosine cofactor.
Step1: The bulged adenosine in domain 6 encounters the 5' splice site, cleaving the 5' exon and forming a lariate intermediate.
Step2: 5', 3' exons ligated together and introns is related as a lariant
Applications
Ribozyme as a Therapeutic Agent
- Ribozymes are capable of specially cleaving RNA molecules.
- Ribozymes are used to inhibit gene expression.
- To study gene function and gene therapy for disease.
- Treatment of disease and cancer.
- The property of ribozyme makes them suitable in the research of genetics and developmental biology.
- Develop new drugs.
- Ribozyme therapy.
Frequently Asked Questions (FAQs)
1. What makes ribozymes essential to biotechnology?
Ribozymes are highly important in biotechnology because they can perform
specific tasks inside cells with high accuracy. Scientists utilize them to research
genes, develop novel medications, and treat ailments.
2. Why was ribozyme discovery significant?
RNA may function as both genetic material and a biological catalyst, as proven
by the discovery of ribozymes. This provided credibility to the RNA world
theory, which postulates that early life might have been totally dependent on
RNA molecules.
Author
Dr. Smita Sisodiya
Assistant Professor,Department of Science
Biyani Group Of Colleges,Jaipur