Disease relevance of ASNS

• In human hepatoma cells cultured in medium containing amino acids, the mRNA of asparagine synthetase is not detectable by RNase protection mapping [1].
• Though the precise molecular mechanisms that result in the appearance of drug resistance are the subject of active study, potent ASNS inhibitors may have clinical utility in treating asparaginase-resistant forms of childhood ALL [2].
• Tissue microarrays confirmed low ASNS expression in a subset of clinical ovarian cancers as well as other tumor types [3].
• Nevertheless, a significant higher portion (p < 0.05) of girls (29%) corresponded to the definition overweight according to ASNS (Austrian Survey of Nutritional Status), while only 20% of the boys felt into the category overweight [4].
• Isolation of human cDNAs for asparagine synthetase and expression in Jensen rat sarcoma cells [5].

High impact information on ASNS

• Significant side effects can arise in these protocols and, in many cases, patients develop drug-resistant forms of the disease that may be correlated with up-regulation of the enzyme glutamine-dependent asparagine synthetase (ASNS) [2].
• The three-dimensional structures of tryptophan synthase, carbamoyl phosphate synthetase, glutamine phosphoribosylpyrophosphate amidotransferase, and asparagine synthetase have revealed the relative locations of multiple active sites within these proteins [6].
• Nucleotide sequence analysis of cDNAs for asparagine synthetase (AS) of Pisum sativum has uncovered two distinct AS mRNAs (AS1 and AS2) encoding polypeptides that are highly homologous to the human AS enzyme [7].
• Asparagine, the primary assimilation product from N2 fixation in temperate legumes and the predominant nitrogen transport product in many plant species, is synthesized via asparagine synthetase (AS; EC 6.3.5.4) [8].
• A role for asparaginyl-tRNA in the regulation of asparagine synthetase in a mammalian cell line [9].

Chemical compound and disease context of ASNS

• The cDNAs containing the entire protein-coding sequence expressed asparagine synthetase activity and were capable of conferring asparagine prototrophy on the Jensen rat sarcoma cells [5].
• Transcription initiation sites of the asparagine synthetase gene were investigated in human hepatoma cells after amino acid limitation by incubation in amino acid-complete minimal essential medium or medium lacking histidine [10].

Biological context of ASNS

• Amino acid deprivation induces the transcription rate of the human asparagine synthetase gene through a timed program of expression and promoter binding of nutrient-responsive basic region/leucine zipper transcription factors as well as localized histone acetylation [11].
• Here we show that overexpression of the bZIP protein ATF5, a transcriptional activator, stimulates asparagine synthetase promoter/reporter gene transcription via the nutrient-sensing response unit [1].
• Immediately following amino acid removal, the kinetics of binding for ATF4, ATF3, and C/EBPbeta itself to the 93 bp regulatory region were similar to those observed for the amino-acid-responsive asparagine synthetase gene [12].
• To assess whether the ovarian relationship is causal, we used RNA interference to silence ASNS in three ovarian lines and observed 4- to 5-fold potentiation of sensitivity to l-ASP with two of the lines [3].
• Cis- and trans-acting elements involved in amino acid regulation of asparagine synthetase gene expression [13].

Anatomical context of ASNS

• Transcription from the ASNS (asparagine synthetase) gene is increased in response to either amino acid (amino acid response) or glucose (endoplasmic reticulum stress response) deprivation [14].
• While this study refined the localization of the gene, it also revealed a rearrangement in a somatic cell hybrid line which was used in previous ASNS mapping [15].
• Molecular profiling of the NCI-60 cancer cell lines using five different microarray platforms showed strong negative correlations of asparagine synthetase (ASNS) expression and DNA copy number with sensitivity to l-ASP in the leukemia and ovarian cancer cell subsets [3].
• Asparagine synthetase cDNAs containing the complete coding region were isolated from a human fibroblast cDNA library [5].
• Compared to asparagine synthetase isolated from beef pancreas, the one expressed in E. coli migrated at a slightly slower rate on a denaturing protein gel [16].

Associations of ASNS with chemical compounds

• Expression of human asparagine synthetase (ASNS), which catalyzes asparagine and glutamate biosynthesis, is transcriptionally induced following amino acid deprivation [11].
• Asparagine synthetase catalyses the glutamine- and ATP-dependent conversion of aspartic acid to asparagine [1].
• Treatment of these transferant cell lines with 5-azacytidine greatly increased the expression of asparagine synthetase mRNA, protein, and activity [5].
• These results confirm the existence of a glutamine amidotransfer domain with an N-terminal cysteine essential for the glutamine-dependent asparagine synthetase activity [17].
• The N-terminal cysteine of human asparagine synthetase is essential for glutamine-dependent activity [17].

Regulatory relationships of ASNS

• Based on sequence analysis, one of the predicted truncated proteins (ATF3deltaZip3) is likely incapable of binding DNA; and yet, exogenous expression of the cDNA enhanced starvation-induced or ATF4-activated ASNS transcription, possibly by sequestering corepressor proteins [14].

Other interactions of ASNS

• Overexpression studies established that ATF4, ATF3-FL, and C/EBPbeta-LAP could coordinately modulate the transcription from the human ASNS promoter [11].
• Collectively, the results provide evidence for a potential role of multiple predicted ATF3 isoforms in the transcriptional regulation of the ASNS gene in response to nutrient deprivation [14].
• Significantly, that potentiation was >700-fold in the multidrug-resistant derivative OVCAR-8/ADR, showing that the causal relationship between ASNS expression and l-ASP activity survives development of classical multidrug resistance [3].
• Additionally, a processed pseudogene for asparagine synthetase was found about 6 kb upstream of the GNAL gene [18].
• We report the transactivation of two genes, asparagine synthetase and human telomerase reverse transcriptase [19].

Analytical, diagnostic and therapeutic context of ASNS

• Chromatin immunoprecipitation analysis provides the first in vivo evidence for activating transcription factor (ATF)-3 binding to the proximal ASNS promoter containing the nutrient-sensing response element-1 sequence [14].
• We have mapped the asparagine synthetase gene (ASNS) to 7q21.3 by fluorescence in situ hybridization [15].
• Accurate detection of asparagine synthetase (ASNS) using quantitative real-time PCR (qRT-PCR), without requiring DNaseI treatment [20].
• Site-specific mutagenesis was used to replace the N-terminal cysteine in human asparagine synthetase by an alanine [17].
• Asparagine synthetase chemotherapy [2].

References