Alternative splicing is the process by which a large number of different mRNAs and proteins are produced from a comparably low number of genes, this occurs in most metazoans. It is believed that around 60% of human genes undergo alternative splicing and many genes have multiple transcripts produced via splicing, some genes have thousands of different transcripts that are able to be produced by this process. The production of these altered mRNAs and proteins can occur due to multiple different changes to the mRNA. One of the main alterations is the inclusion or exclusion of cassette exons. These are exons are not constitutive and are only sometimes included in the transcript. The length of exons can also be altered by changes of the location of one of the genes splice sites. These changes in splice site location can have many different effects on the protein produced from the transcript such as enzymatic activity and localisation within the cell. The process of splicing is directed by splice site sequences which are observed at the junction between the intron and exon. These splice sites are found at both the 5’ end and 3’ end of introns and both contain consensus sequences to which the spliceosome can attach. The spliceosome is a large macromolecular complex that assembles around the splice site from five small nuclear ribonuleoproteins as well as multiple accessory proteins Splicing occurs through a reaction which contains two transesterification steps which are catalysed by the spliceosome. (maybe insert more about mechanism) (need references)

Research by Webby et.al (2009) using liquid chromatography-mass spectrometry techniques found a link between Jmjd6 function and the RNA splicing mechanism. Jmjd6 was observed to hydroxylate lysine residues on a key splicing regulatory factor in humans called U2AF65. It was found that Jmjd6 hydroxylated two specific lysine residues which as Lys15 and Lys276. These findings suggest a role in the regulation of alternative splicing by jmjd6.

RNA polymerase pause release-

RNA polymerase II pausing occurs during early transcriptional elongation after the enzyme has bound the RNA strand. At this point further signals are required for elongation to continue. Until these signals are released the RNA polymerase remains stably bound to the RNA. After the signals are released the polymerase then progresses along the gene, terminates and eventually restarts transcription. The process of polymerase II pausing is prevalent in metazoans and has been suggested as a widespread mecha