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Small nuclear ribonucleoprotein complexes (abbreviated as U-snRNP) are essential for splicing of precursor mRNA molecules. U1-snRNP is the most abundant RNP particle in the nucleus and consists of one small uridylate-rich RNA (U1 RNA) complexed with several proteins: the three 68/70 kDa, A, C polypeptides are unique to the U1-snRNP particle, whereas 7 so-called Sm proteins (B/B', D1, D2, D3, E, F, G) form a core subparticle that is common to all U-snRNP complexes.
Both the U1-specific proteins and the Sm core particle are targets of autoantibodies which classically have been called the RNP and RNP-Sm specificities, respectively. A clean diagnostic distinction of these specificities has been complicated by the biochemical difficulties of producing clean subparticle fractions from native sources. The use of single recombinant proteins as antigenic targets guarantees a much higher sensitivity and specificity and is the only way to determine RNP antibodies sensu stricto without the disturbing influence of Sm antigens; also with single U1 proteins antibodies will be detected which can be missed because of steric hindrance when using the RNP-Sm complex in an assay.
Autoantibodies to U1-snRNP are present in 95% of patients with Mixed Connective Tissue Disease (MCTD) and 30% of patients with SLE. Antibodies against the 68/70 kDa protein are known to have a high clinical significance in MCTD patients. The 68/70 kDa nomenclature of this protein refers to the fact that different splice variants of the protein are found in human cells.

SNRPD2 is a member of the small nuclear ribonucleoprotein core protein family. SNRPD2 is a small nuclear ribonucleoprotein (snRNPs) which comprises the spliceosome in eukaryotes. SNRPD2 is required for pre-mRNA splicing and small nuclear ribonucleoprotein biogenesis.

Chemokine (C-C motif) ligand 6 (CCL6) is a small cytokine belonging to the CC chemokine family that has only been identified in rodents.
In mice, CCL6 is expressed in cells from neutrophil and macrophage lineages, and can be greatly induced under conditions suitable for myeloid cell differentiation. It is highly expressed in bone marrow cultures that have been stimulated with the cytokine GM-CSF. Some low levels of gene expression also occur in certain cell lines of myeloid origin (e.g. the immature myeloid cell lines DA3 and 32D cl3, and the macrophage cell line P388D) that can also be greatly induced in culture with GM-CSF. However, in activated T cell lines, expression of CCL6 is greatly reduced. CCL6 can also be induced in the mouse lung by the cytokine interleukin 13. Mouse CCL6 is located on chromosome 11. The cell surface receptor for CCL6 is believed to be the chemokine receptor CCR1.

The bone morphogenetic proteins (BMPs) are a family of secreted signaling molecules, which can induce ectopic bone growth. Various BMPs are part of the transforming growth factor-beta (TGFB) superfamily. BMPs were initially identified by an ability of demineralized bone extract to induce endochondral osteogenesis in vivo in an extraskeletal site. Based upon its expression early in embryogenesis, BMP6 has a suggested role in early development. Moreover, the fact that the BMP6 is closely related to BMP5 and BMP7 leads to an assumption of possible bone inductive activity.

EXO2 is a 3'-to-5' exonuclease specific for small (primarily 5 nucleotides or less in length) single-stranded RNA and DNA oligomers. RNA Exonuclease 2 (REXO2) takes part in DNA repair, replication, and recombination, and in RNA processing and degradation. EXO2 is involved in resistance of human cells to UV-C-induced cell death via its part in the DNA repair process.

SNRPA associates with stem loop II of the U1 small nuclear ribonucleoprotein, which binds the 5' splice site of precursor mRNAs and is essential for splicing. The SNRPA protein autoregulates itself by polyadenylation inhibition of its own pre-mRNA via dimerization and is involved in the coupling of splicing and polyadenylation. SNRPA binds stem loop II of U1 snRNA. SNRPA is the first snRNP to interact with pre-mRNA. This interaction is vital for the subsequent binding of U2 snRNP and the U4/U6/U5 tri-snRNP.

Fibroblast Growth Factor-6 (FGF6) belongs to the fibroblast growth factor (FGF) family. FGF family members possess extensive mitogenic and cell survival functions, and are involved in various biological processes, including embryonic development, cell growth, morphogenesis, tissue repair, tumor growth and invasion. The FGF6 gene displayes oncogenic transforming activity when transfected into mammalian cells. The mouse homolog of the FGF6 gene displays a restricted expression profile predominantly in the myogenic lineage, suggesting a role in muscle regeneration or differentiation.

RPL22, a cytoplasmic ribosomal protein, is a member of the L22E family of ribosomal proteins and a component of the 60S subunit. RPL22 binds specifically to Epstein-Barr virus-encoded RNAs (EBERs) 1 and 2.

HCV is a small 50nm, enveloped, single-stranded, positive sense RNAvirus in the family Flaviviridae.
HCV has a high rate of replication with approximately one trillion particles produced each day in an infected individual. Due to lack of proofreading by the HCV RNA polymerase, the HCV has an exceptionally high mutation rate, a factor that may help it elude the host's immune response. Hepatitis C virus is classified into six genotypes(1-6) with several subtypes within each genotype. The preponderance and distribution of HCV genotypes varies globally. Genotype is clinically important in determining potential response to interferon-based therapy and the required duration of such therapy. Genotypes 1 and 4 are less responsive to interferon-based treatment than are the other genotypes (2, 3, 5 and 6).

GF-like family receptor 1 (IGFLR1) is encoded by a gene mapping to human chromosome 19. IGFLR1 which is cell membrane receptor for the IGF-like family proteins binds IGFL1 and IGFL3 with a higher affinity and may as well bind IGFL2.

Protein Phosphatase 1, Regulatory Subunit 8 (PPP1R8) is the RNA-binding subunit of a key species of protein phosphatase-1 in the nucleus. The PPP1R8 enzyme is an inhibitor subunit of the main nuclear protein phosphatase-1 (PP-1). PPP1R8 has RNA-binding activity however it doesn’t cleave RNA and may target PP-1 to RNA-associated substrates. Two isoforms of the PPP1R8 protein are specific inhibitors of type 1 serine/threonine protein phosphatases which can bind but not cleave RNA. The third isoform of the PPP1R8 protein is deficient in of the phosphatase inhibitory activity nonetheless it is a single-strand endoribonuclease comparable to RNase E of E. coli.

IFIH1 is a DEAD box protein which is upregulated in response to treatment with beta-interferon and a protein kinase C-activating compound, mezerein. Irreversible reprogramming of melanomas can be attained by therapy with both these agents; treatment with either agent alone only achieves reversible differentiation. DEAD box proteins are implicated in several cellular processes involving alteration of RNA secondary structure such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly.

SNRPC is a member of the U1 small nuclear ribonucleoprotein C family. The SNRPC protein component of the U1 small nuclear ribonucleoprotein (snRNP) particle required for the formation of the spliceosome. SNRPC participates in the processing of nuclear precursor messenger RNA splicing. snRNP particles are tackled by autoantibodies frequently produced by patients with connective tissue diseases.

EXO2 is a 3'-to-5' exonuclease specific for small (primarily 5 nucleotides or less in length) single-stranded RNA and DNA oligomers. RNA Exonuclease 2 (REXO2) takes part in DNA repair, replication, and recombination, and in RNA processing and degradation. EXO2 is involved in resistance of human cells to UV-C-induced cell death via its part in the DNA repair process.

Eukaryotic initiation factor 4A-III (EIF4A3) is a member of the DEAD box helicase family and eIF4A subfamily. DEAD box proteins, distinguished by the conserved motif Asp-Glu-Ala-Asp (DEAD), are putative RNA helicases. These proteins are involved in several cellular processes including alteration of RNA secondary structure, such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly. EIF4A3 is a part of a splicing-dependent multiprotein exon junction complex (EJC) accumulated at splice junction on mRNAs. Based upon their distribution patterns, some members of the DEAD box helicase family are thought to be involved in embryogenesis, spermatogenesis, and cellular growth and division.

U2 small nuclear ribonucleoprotein A (SNRPA1), a 255 amino acid protein, is a component of the U2 snRNP which forms a complex with U2 snRNP B (U2B). U2 snRNP A and U2 snRNP B form together a complex which binds to the U2 snRNA hairpin IV. The configuration of the U2 snRNP A/U2 snRNP B dimer and the delicate variations of a few key residues regulate the snRNP-RNA-binding specificity.

CTD small phosphatase-like protein (CTDSPL) specially catalyzes the dephosphorylation of 'Ser-5' within the tandem 7 residues repeats in the C-terminal domain (CTD) of the biggest RNA polymerase II subunit POLR2A. CTDSPL negatively regulates RNA polymerase II transcription, probably by directing the transition from initiation/capping to processive transcript elongation. CTDSPL is employed by REST to neuronal genes which contain RE-1 elements, directing to neuronal gene silencing in non-neuronal cells.

Small Nuclear RNA Activating Complex, Polypeptide 1 (SNAPC1) is a part of the SNAPc complex necessary for the transcription of both RNA polymerase II and III small-nuclear RNA genes. SNAPC1 binds to the proximal sequence element (PSE), a non-TATA-box basal promoter element common to these 2 types of genes. Moreover, SNAPC1 recruits TBP and BRF2 to the U6 snRNA TATA box.

SARS-Associated Coronavirus Nuclecapsid is an enveloped viral componentthat contains three external structural antigens, the mains are membrane (M), envelope (E), and spike (S) proteins. Spike (S)-glycoprotein of the virus interacts with a membrenal receptor and mediates membrane fusion to grant viral entry into the target cells. therefore, S-protein has a crucial part in virus infection cycle and is the main target of neutralizing antibodies.

RDBP is a putative RNA binding protein. RDBP protein is one of the five components of the multisubunit NELF complex which collaborates with DSIF to repress RNA polymerase II elongation. Control of transcription elongation needs a complex interaction between positive transcription elongation factor b and negative transcription elongation factors, DSIF and NELF. DSIF and NELF, act as negative transcription elongation factors by increasing the time the polymerase spends at pause sites. RDBP has a functional RNA-binding domain, whose mutations impair transcription repression without affecting known protein-protein interactions.

NHP2L1 is a member of the ribosomal protein L7Ae family. NHP2L1 protein limited to the nucleus, primarily focused in the dense fibrillar component of the nucleolus. NHP2L1 directly binds to the 5' stem-loop of U4 snRNA and has a vital part in the late stage of spliceosome assembly, prior to step I of splicing catalysis.

SARS Coronavirus is an enveloped virus containing three outer structural proteins, namely the membrane (M), envelope (E), and spike (S) proteins. Spike (S)-glycoprotein of the virus interacts with a cellular receptor and mediates membrane fusion to allow viral entry into susceptible target cells. Accordingly, S-protein plays an important role in virus infection cycle and is the primary target of neutralizing antibodies.

The SARS Nucleocaspid is a protein that has a crucial structural importance, by making the virions associates with the RNA genome and therefore create a nucleocapsid that has the specific helical form. There has been found 3 different domain structures to the nucleocapsid antigen. This protein contains 3 outer structural proteins, the membrane (M), envelope (E), and spike (S) proteins.