Review Question - QID 100089

The clinical presentation is consistent with systemic lupus erythematosus (SLE) in which patients can have anti-snRNP antibodies. snRNPs, or small nuclear ribonucleoprotein particles, are parts of the spliceosome, the molecule that removes introns from mRNA before it is transferred out of the nucleus.

Introns (INternvening sequences) must be removed since they will not be expressed in the final protein. snRNPs are part of a spliceosome complex that mediates the RNA editing. During this process a lariat is formed and adjacent exons are attached to one another. RNA splicing also allows for alternative splicing, in which one hnRNA can be spliced differently to produce different protein products.

Hoffman et al. state that dysregulated apoptosis and inappropriate stimulation of nucleic acid-sensing receptors may lead to loss of tolerance against the protein components of such complexes, activation of autoreactive T cells and formation of autoantibodies. This has been demonstrated to occur in SLE and seems to represent a general mechanism that may be crucial for the development of systemic autoimmune diseases.

Gill et al. discuss diagnosis of SLE and note that more commonly seen antibodies are antinuclear antibodies (ANA) and anti-dsDNA, yet presence of these antibodies has little diagnostic value in the absence of symptoms.

Illustration A is a schematic of RNA splicing with snRNPs.

Incorrect Answers:
Answer 1: Before transcription is finished, a methylated transferase adds a 5' 7-methylguanosine cap on the mRNA.
Answer 2: Poly-A-polymerase adds the poly-A-tail.
Answer 3: Both the 5' and 3' modifications protect mRNA from degradation.
Answer 5: Transcription is not related to splicesome.