Abstract
Prior to the completion of the human genome project, the human genome was thought to have a greater number of genes as it seemed structurally and functionally more complex than other simpler organisms. This along with the belief of “one gene, one protein”, were demonstrated to be incorrect. The inequality in the ratio of gene to protein formation gave rise to the theory of alternative splicing (AS). AS is a mechanism by which one gene gives rise to multiple protein products. Numerous databases and online bioinformatic tools are available for the detection and analysis of AS. Bioinformatics provides an important approach to study mRNA and protein diversity by various tools such as expressed sequence tag (EST) sequences obtained from completely processed mRNA. Microarrays and deep sequencing approaches also aid in the detection of splicing events. Initially it was postulated that AS occurred only in about 5% of all genes but was later found to be more abundant. Using bioinformatic approaches, the level of AS in human genes was found to be fairly high with 35-59% of genes having at least one AS form. Our ability to determine and predict AS is important as disorders in splicing patterns may lead to abnormal splice variants resulting in genetic diseases. In addition, the diversity of proteins produced by AS poses a challenge for successful drug discovery and therefore a greater understanding of AS would be beneficial.
Highlights
With the completion of the human genome project, new insights into genomic data have been made possible
From the abundance of alternative splicing (AS) seen in higher eukaryotes, it is probable that many features of the cell phenotype, including those that lead to tumour development, are monitored by the relative expression of the AS isoforms of several genes [19]
Transcriptional regulation of the promoter mainly results in variations in the amount of RNA generated, producing N-terminal protein variants by different transcriptional start sites
Summary
With the completion of the human genome project, new insights into genomic data have been made possible. Sequence-based and microarray-based analyses have shown that AS events are more commonly observed in transcripts present in those genes of functionally complex tissues having varied cell types like the brain and testis [10]. Several complex examples have been identified including the neurexin and CD44 loci, which have two or more AS sites, with the autonomy of AS cassettes thought to form several protein accumulations encoded by a single locus [14, 15] Another example is the Drosophila gene Dscam, which encodes the axon guidance receptor and is able to produce approximately 38, 016 different protein isoforms [14, 16]. From the abundance of AS seen in higher eukaryotes, it is probable that many features of the cell phenotype, including those that lead to tumour development, are monitored by the relative expression of the AS isoforms of several genes [19]
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