SAAL1

Protein-coding gene in the species Homo sapiens

SAAL1

Identifiers
Aliases| SAAL1, SPACIA1, serum amyloid A like 1
External IDs| MGI: 1926185; HomoloGene: 34706; GeneCards: SAAL1; OMA:SAAL1 - orthologs
| Gene location (Human)

Chr.| Chromosome 11 (human)[1]

Band| 11p15.1| Start| 18,069,935 bp[1]
End| 18,106,087 bp[1]
| Gene location (Mouse)

Chr.| Chromosome 7 (mouse)[2]

Band| 7|7 B3| Start| 46,335,532 bp[2]
End| 46,360,104 bp[2]
| RNA expression pattern

Bgee| | Human| Mouse (ortholog)

|

| Top expressed in

* gonad

* ganglionic eminence

* ventricular zone

* mucosa of ileum

* testicle

* tibialis anterior muscle

* cerebellar hemisphere

* right hemisphere of cerebellum

* Achilles tendon

* left ovary

| Top expressed in

* Ileal epithelium

* maxillary prominence

* mandibular prominence

* gastrula

* medial ganglionic eminence

* epiblast

* tail of embryo

* otic placode

* saccule

* abdominal wall

More reference expression data
BioGPS| | n/a

| Orthologs

Species| Human| Mouse
Entrez| |

113174

78935

Ensembl| |

ENSG00000166788

ENSMUSG00000006763

UniProt| |

Q96ER3

Q9D2C2

RefSeq (mRNA)| |

NM_138421

NM_030233

RefSeq (protein)| |

NP_612430

NP_084509

Location (UCSC)| Chr 11: 18.07 – 18.11 Mb| Chr 7: 46.34 – 46.36 Mb
PubMed search| [3]| [4]
Wikidata
| View/Edit Human| View/Edit Mouse

|

Serum amyloid A-like 1 (also known as SAAL1, Synoviocyte proliferation-associated in collagen-induced arthritis 1, and SPACIA1) is a protein in humans encoded by the SAAL1 gene.[5][6]

## Gene

[edit]

### Locus

[edit]

The human SAAL1 gene is located at position 11p15.1 on the minus strand spanning from base pairs 18080292-18106082 (25,790 bases).[5] It has 12 exons and 11 introns and encodes a single isoform.[5][7]

Members of the serum amyloid-A family such as SAA1 reside in the same loci as SAAL1.[7]

SAAL1 gene neighborhood at loci 11p15.1[8]

### Promoter

[edit]

The promoter region (GXP_169676) is predicted to span from basepairs 18105980-18107207 and extends into the first exon of SAAL1.[9] Predicted transcription factors include TATA binding factors, NF-κB, and KLF4, KLF5, and KLF6.[10]

### Expression

[edit]

SAAL1 is ubiquitously expressed at moderate levels across all human tissues with highest expression in testes as determined by RNA-sequencing and microarray expression profiling.[11][12]

## Transcript

[edit]

Predicted 5' UTR binding proteins of the human SAAL1 transcript include SRSF3 and FXR2.[13] Predicted 3' UTR binding proteins include SRSF5 and U2AF2.[13] All predicted proteins are involved in mRNA splicing, export, and translation.[14][15][16][17]

SAAL1 mRNA sequence and translated amino acid sequence. Exon boundaries, start and stop codons, motifs, and post-translational modifications are annotated. Well conserved base pairs and amino acids are bolded

## Protein structure

[edit]

I-TASSER generated model of SAAL1 tertiary structure. The N-terminus is blue and C-terminus is red.[18][19][20]

### General properties

[edit]

The SAAL1 protein has a single known isoform consisting of 474 amino acids with a molecular weight of 53.5 kDa.[5] The unmodified SAAL1 protein is acidic with an isoelectric point of 4.4.[21]

### Composition

[edit]

SAAL1 is abundant in aspartic acid (7.8% by composition) and deficient in glycine (3.4% by composition)compared to other human proteins.[22] It also has 44 more aspartic acid and glutamic acid residues compared to lysine and arginine, indicating an overall negative charge.[23] Two negatively charged and glutamic acid abundant segments were identified and labeled in the SAAL1 conceptual translation.[22]

### Domains and motifs

[edit]

SAAL1 contains an armadillo-like fold with an enveloped fungal symportin-1 like region.[24][25] Other motifs were predicted by ELM[26] and MyHits Motif Scan.[27]

Predicted Motifs  Predicted Motifs  | Amino Acids  | Tools

|
|

Casein kinase 2 phosphorylation site  | 152-155, 165-168  | MyHits,[27] ELM[26]
Nuclear Export Signal | 72-84  | ELM[26]
MAPK docking site  | 106-115, 344-352  | ELM[26]

### Sub-cellular localization

[edit]

Immunofluorescent staining has identified SAAL1 localization in the nucleus of Caco-2 cells.[28] However, western blotting of hepatocellular carcinoma cell lines identified SAAL1 localization in the cytoplasm with minor amounts in the cell membrane and nucleus.[29]

### Post-translational modifications

[edit]

SAAL1 undergoes phosphorylation at two experimentally verified sites: Ser6 and Thr387.[25] Predicted post-translational modifications are detailed in the following table.

Predicted Post-Translational Modifications  Tool  | Predicted Modification  | Amino Acids

|
|

NetPhos[30][31] | Casein kinase 2 phosphorylation | Thr152, Ser165
YinOYang[32][33] | O-linked glycosylation | Ser6
SMART[34] | Ubiquitination | Lys209, Val302

## Clinical significance

[edit]

SAAL1 overexpression has been correlated with the proliferation of rheumatoid and osteoarthritic synovial fibroblasts as well as disease progression.[24][35] RNAi knockouts of SAAL1 reduced arrested fibroblasts in G0/G1 phase and reduced proliferation by 20% with a 50% reduction when fibroblasts were stimulated by TNF-α.[24] Stability assays reveal that SAAL1 promotes G1/S transition via CDK6 mRNA stabilization.[24][35] This finding was corroborated by SAAL1 knockdowns in hepatocellular carcinomas which also demonstrated impaired HGF-induced migration and increased sensitivity to sorafenib and foretinib treatment.[29] Additionally, SAAL1 is overexpressed in hepatocellular carcinoma cells and in chondrocytes stimulated by interleukin-1 beta, but this effect is diminished in the presence of glucosamine.[29][36]

Studies of the rock bream SAAL1 ortholog noted an increase in gene expression in response to bacterial and viral pathogens.[37] Human SAAL1 has been reported to interact with the M protein of SARS-Cov-2,[38] Orf4 of Kaposi's sarcoma-associated herpesvirus,[39] and the M and M2 proteins of influenza A.[40] It has also been reported as an interferon stimulator and TRIM25 interactor.[41][42] Other interacting proteins include PNKD (which plays a role in cardiac hypertrophy via NF-κB signaling),[43][44] TMIGD3(which inhibits NF-κB activity),[45][46] and MARK3.[47]

## Evolution

[edit]

### Homology

[edit]

Three page PDF of multiple sequence alignment of vertebrate SAAL1 orthologs referenced in the orthologs table.[22][48]

BLAST searches have found homologs for SAAL1 in organisms as distant as plants, though few orthologs were found for fungi.[49] The following table provides a sample of the ortholog space. Vertebrate orthologs share >50% identity with human protein SAAL1 while displayed invertebrates and non-metazoan orthologs have 30% or less identity.

Sample of SAAL1 Orthologs  Species  | Organism Common Name  | Multiple Sequence Alignment Abbreviation  | Date of Divergence from Humans

(Millions of Years Ago)[50]

| Length (AAs)  | Identity  | NCBI Accession

|
|
|
|
|
|

Homo sapiens | Humans | Hsa_SAAL1  | 0  | 474  | 100  | NP_612430.2
Macaca mulatta | Rhesus Monkey | Mmu_SAAL1  | 29  | 473  | 98  | XP_001087433.2
Ictidomys tridecemlineatus | Thirteen-Lined Ground Squirrel | Itr_SAAL1  | 90  | 474  | 90  | XP_005326805.1
Monodelphis domestica | Gray Short-Tailed Opossum | Mdo_SAAL1  | 159  | 475  | 73  | XP_007497074.1
Ornithorhynchus anatinus | Platypus | Oan_SAAL1  | 177  | 486  | 71  | XP_028915648.1
Calidris pugnax | Ruff | Cpu_SAAL1  | 312  | 472  | 70  | XP_014815565.1
Rhinatrema bivittatum | Two-Lined Caecilian | Rbi_SAAL1  | 352  | 472  | 61  | XP_029438391.1
Erpetoichthys calabaricus | Reedfish | Eca_SAAL1  | 435  | 484  | 50  | XP_028650019.1
Callorhinchus milii | Australian Ghost Shark | Cmi_SAAL1  | 473  | 474  | 54  | XP_007885592.1
Saccoglossus kowalevskii | Acorn Worm | Ski_SAAL1  | 684  | 508  | 28  | XP_002732678.2
Pomacea canaliculata | Golden Apple Snail | Pca_SAAL1  | 797  | 563  | 30  | XP_025086883.1
Orbicella faveolata | Mountainous Star Coral | Ofa_SAAL1  | 824  | 561  | 25  | XP_020625180.1
Rhizopus microsporus | (a fungal plant pathogen)  | Rmi_SAAL1  | 1105  | 323  | 14  | XP_023467779.1
Phycomyces blakesleeanus | (a type of fungus)  | Pbl_SAAL1  | 1105  | 346  | 14  | XP_018285622.1
Manihot esculenta | Cassava | Mes_SAAL1  | 1496  | 536  | 20  | XP_021611223.1
Lactuca sativa | Lettuce | Lsa_SAAL1  | 1496  | 534  | 19  | XP_023753062.1
Lupinus angustifolius | Narrowleaf Lupin | Lan_SAAL1  | 1496  | 488  | 18  | XP_019436310.1
Elaeis guineensis | Oil Palm | Egu_SAAL1  | 1496  | 568  | 18  | XP_010933466.1
Phalaenopsis equestris | (a type of orchid)  | Peq_SAAL1  | 1496  | 551  | 17  | XP_020591929.1
Phoenix dactylifera | Date Palm | Pda_SAAL1  | 1496  | 508  | 17  | XP_026661658.1

SAAL1 exists in up to four isoforms in other vertebrates. Across these orthologs, it is the only member of its gene family.

Two page PDF of multiple sequence alignment of invertebrate and non-metazoan SAAL1 orthologs in the table, excluding the fungi orthologs. Poorly aligned regions are not shown.[22][48]

A multiple sequence alignment of the vertebrate homologs demonstrated high conservation of the protein, especially in the armadillo-type fold and fungal symportin-1 like motif. An alignment of invertebrate and non-metazoan orthologs indicates drastic changes in the protein's primary structure, but some conservation in the labeled motifs. Highly similar amino acids were colored red and less similar amino acids were colored blue; "*" denotes conservation and "." denotes similarity.

### Phylogeny

[edit]

The date of divergence from the human ortholog was compared to the corrected % divergence for SAAL1 orthologs. Compared against data for cytochrome c and fibrinogen alpha proteins in similar orthologs, SAAL1 evolved at a moderate rate.

SAAL1 evolutionary rate vs fibrinogen alpha and cytochrome c.

## References

[edit]

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