What is the Difference Between Cis and Trans Splicing?

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The key difference between cis and trans splicing lies in the molecular mechanism: cis splicing is an intramolecular process, while trans splicing is an intermolecular process. Both mechanisms involve the removal of introns or outrons and the joining of exons to form mature mRNA molecules, but they differ in the way they handle the RNA transcripts.

In cis splicing:

  • The splicing process removes introns and joins exons within the same RNA transcript.
  • The 5' splice site is present on the pre-mRNA for U1 snRNP binding.
  • This mechanism is an intramolecular process, meaning it occurs within a single RNA molecule.

In trans splicing:

  • The splicing process generates a single RNA transcript from multiple separate pre-mRNAs.
  • There is no 5' splice site on the pre-mRNA for U1 snRNP binding; instead, the 5' splice site is provided by the spliced leader (SL) sequence.
  • This mechanism is an intermolecular process, meaning it involves multiple RNA molecules.

In summary, cis splicing involves the removal of introns and the joining of exons within a single RNA transcript, while trans splicing involves the same processes but with multiple separate pre-mRNAs.

Comparative Table: Cis vs Trans Splicing

Here is a table summarizing the differences between cis and trans splicing:

Feature Cis Splicing Trans Splicing
Definition Cis splicing is an intramolecular mechanism that removes introns and joins the exons within the same RNA transcript. Trans splicing is an intermolecular mechanism that removes introns or outrons and joins the RNA transcripts.
Splicing Process In cis splicing, introns are removed to form mature mRNA. In trans splicing, introns or outrons are removed to form mature mRNA.
RNA Transcripts Cis splicing involves a single RNA transcript. Trans splicing involves two separate RNA transcripts.
Splice Site Consensus Sequences Cis splicing sites have the same splice site consensus sequences as trans splicing sites.
Splicing Machinery Both cis and trans splicing utilize similar splicing machinery.

Cis splicing is the typical splicing process of pre-mRNA carried out by spliceosomes, while trans splicing is a less common process that involves two separate RNA transcripts.