Disease relevance of HTN3

• A 39-kb region of DNA containing the HIS1 and HIS2 genes was isolated from two human genomic phage libraries as a series of overlapping clones [1].
• Our data demonstrate that a key determinant in the mechanism of Hst 5 toxicity in C. albicans cells is the disruption of regulatory circuits for cell volume homeostasis that is closely coupled with loss of intracellular ATP [2].
• We have constructed recombinant adenovirus vectors that contain the histatin 3 cDNA [3].
• Histatins are a family of basic histidine-rich proteins present in human saliva which have therapeutic potential in the treatment of oral candidiasis [4].
• An oligonucleotide primer specific for a conserved amino acid region of the Cys2/His2 zinc finger proteins was used in conjunction with mRNA differential display to amplify related mRNAs from a human ovarian cancer cell line [5].

High impact information on HTN3

• The deduced amino acid sequence shows that the encoded protein, EPF1, contains two repeats of a Cys2/His2 zinc finger motif [6].
• Using simultaneous Hoechst 33342 (Hst) and Pyronin Y (PY) staining for determination of DNA and RNA content, respectively, human CD34(+) cells were isolated in subcompartments of the G0 /G1 phase of the cell cycle by flow cytometric cell sorting [7].
• To test the hypothesis that primitive LTHC-ICs would reenter a state of relative quiescence after in vitro division, BM CD34(+) cells proliferating in ex vivo cultures were identified from their quiescent counterparts by a relative loss of membrane intercalating dye PKH2, and were further fractionated with Hst and PY [7].
• They include, with the exception of histatin 4, all the known histatin 3 fragments, namely histatins 5-12 and the peptides corresponding to 15-24, 26-32, 29-32 residues, and 13 new fragments corresponding to 1-11, 1-12, 1-13, 5-13, 6-11, 6-13, 7-11, 7-12, 7-13, 14-24, 14-25, 15-25, and 28-32 residues of histatin 3 [8].
• Carbonyl cyanide p-chlorophenylhydrazone, dinitrophenol, and azide inhibited Hst 5-induced ATP efflux, thus establishing a correlation between ATP release and cell killing [9].

Chemical compound and disease context of HTN3

• These results suggest that histatin 3 may have potential as an effective antifungal agent, particularly in the treatment of oral candidiasis in HIV-infected patients and patients with AIDS in which resistance to the commonly used antifungal drug fluconazole has emerged [4].

Biological context of HTN3

• Nucleotide sequence analysis of the human salivary protein genes HIS1 and HIS2, and evolution of the STATH/HIS gene family [1].
• The amino acid sequences of histatins 7-12 formally correspond to residues 12-24, 13-24, 12-25, 13-25, 5-11, and 5-12, respectively, of histatin 3, but could also arise proteolytically from histatin 5 or 6 [10].
• Indeed, a low extracellular salt concentration was essential for cell death to occur, even when histatin 3 was already bound to the cell [11].
• A single histatin 3 binding site with a K(d) = 5.1 microM was detected [11].
• This novel process of fungicidal activity by a human salivary protein has highlighted potential interactions of Hst 5 with volume regulatory mechanisms and the process of yeast cell cycle control [2].

Anatomical context of HTN3

• Binding to the spheroplasts was saturable and could be competed with unlabeled histatin 3 [11].
• Human submandibular gland statherin and basic histidine-rich peptide are encoded by highly abundant mRNA's derived from a common ancestral sequence [12].
• Analysis of the magnitude and time course of Hst-induced calcein release from C. albicans cells further showed that loss of cell integrity was a secondary effect following cell death, rather than the result of primary disruption of the yeast cell membrane [13].
• Furthermore, C. albicans cells were respiring and had polarized membranes at least 80 min after ATP release, thus implying a non-lytic exit of cellular ATP in response to Hst 5 [9].
• Transfer of a gene encoding the anticandidal protein histatin 3 to salivary glands [3].

Associations of HTN3 with chemical compounds

• H3 becomes much more ordered in a mixture of 50:50 H2O-dimethyl sulfoxide as indicated by the numerous NOEs, including several side chain to side chain and side chain to backbone connectivities [14].
• Three inhibitors of mitochondrial metabolism: carbonyl cyanide p-chlorophenylhydrazone, dinitrophenol, and azide inhibited Hst 5 killing of Candida albicans, while not inhibiting cellular ATP production [9].
• Consistent with this hypothesis, purinergic agonists BzATP and adenosine 5'O-(thiotriphosphate) induced loss of C. albicans cell viability and purinergic antagonists prevented Hst 5 killing [9].
• Subtle changes in overall conformation are seen with the addition of Cu(2+) to both H3 and H5 [15].
• H3 and H5 formed high affinity complexes with Cu(2+) and Ni(2+) and, to a lesser extent, with Zn(2+) [15].

Regulatory relationships of HTN3

• When the histatin 3 uptake into cells was inhibited by monodansylcadaverine or when histatin 3 binding to HSC70 was precluded by 15-deoxyspergualin, DNA synthesis by histatin 3 was approximately 2-fold less than that without monodansylcadaverine or 15-deoxyspergualin [16].

Other interactions of HTN3

• The structural data suggest that histatins 1 and 3 are derived from different structural genes, whereas histatin 5 is a proteolytic product of histatin 3 [17].
• The molecular cloning of sequences encoding human submandibular gland (SMG) statherin and a basic histidine-rich peptide is described [12].
• Cells with intracellularly expressed Hst 5 had greatly reduced G(1) cyclin transcript levels, indicating that they arrested in the G(1) phase before the onset of Start [2].
• Salivary protein polymorphism was studied in 200 schoolboys, mainly Kisii and Luo from Kenya, East Africa. The frequencies of PR, PA, DB, PB and AMY1 genes were as follows: PR*1: 0.66, PA*(+): 0.18, DB*(+): 0.55, PB*2: 0.12, AMY1*A2: 0.008, AMY1*E: 0.03 [18].
• Hst 5 and HNP-1 are basic proteins of about 3 kDa; however, they have unique primary sequences and solution structures that cannot explain how these two molecules act so similarly on C. albicans to induce cell death [19].

Analytical, diagnostic and therapeutic context of HTN3

• Conformational studies of the salivary peptides histatin 3 (H3) and histatin 5 (H5) were performed by NMR and circular dichroism (CD) in aqueous and nonaqueous solutions [14].
• Following expression of Hst 5, the smallest cells sorted by fluorescence-activated cell sorting from the total population did not replicate and were exclusively in the G(1) phase [2].
• Sequence analysis revealed strong homology between the statherin and basic histidine-rich mRNA's, suggesting their evolution from a common ancestral sequence [12].
• However, Western blot analysis failed to detect specifically increased protein carbonylation in Hst 5-treated cells [20].
• Evaluation of the metal binding properties of the histidine-rich antimicrobial peptides histatin 3 and 5 by electrospray ionization mass spectrometry [15].

References