High impact information on ARF3

• This factor was purified and identified as two small GTP-binding proteins, ARF1 and ARF3 [1].
• Brefeldin A-inhibited guanine nucleotide-exchange proteins (BIG) 1 and BIG2 activate human ADP-ribosylation factors (ARF) 1 and ARF3 by catalyzing the replacement of ARF-bound GDP with GTP to regulate Golgi vesicular transport [2].
• ARF 1 accumulated in microsomes plus Golgi and Golgi fractions, whereas ARF 5 seemed to localize more specifically in Golgi; the smaller increment in ARF 3 was distributed more evenly among fractions [3].
• The ability of certain mutants of ARF3 to alter Golgi morphology without changes in PLD1 activity or COP-I binding is interpreted as evidence for at least one additional, currently unidentified, effector for ARF action at the Golgi [4].
• Arfaptin 1, a approximately 39-kDa protein based on the deduced amino acid sequence, had been initially identified in a yeast two-hybrid screen using dominant active ARF3 (Q71L) as bait with an HL-60 cDNA library [5].

Biological context of ARF3

• Employing yeast two-hybrid screening of an HL60 cDNA library using a constitutively active mutant of ARF3 (ARF3.Q71L), as a probe, we have identified a cDNA encoding a novel protein with a calculated molecular mass of 38.6 kDa, which we have named arfaptin 1 [6].
• Sequences of two overlapping genomic clones indicated that the ARF 3 gene spans approximately 18.3 kb and contains five exons and four introns [7].
• The latter encodes the COOH-terminal 53 amino acids of ARF 3 and contains greater than 2500 base pairs of untranslated DNA [7].
• The 1.2-kb ARF 3 mRNA is shown to arise by use of an alternative polyadenylation signal (AACAAA) at nucleotide 1091 within the ARF 3 cDNA [7].
• A screen for mutations in Arf3 that specifically lost the ability to bind MKLP1 identified 10 of 14 point mutations in the GTP-sensitive switch I or switch II regions of Arf3 [8].

Anatomical context of ARF3

• The relative expression of ARFs in endothelial cells thus differs from that in neuronal tissues where it had been found that ARF3 is the predominant species [9].
• In addition, the ARF3 protein was developmentally regulated in the mammary gland with the highest levels in virgin and post-weaning glands [10].
• Together, these findings suggest for the first time that stimulation of ARF3 expression, subcellular redistribution and interaction with acetylated histone H3 may play a role in the action of HRG in mammary epithelial cells [10].
• Also, HRG triggered a rapid redistribution of ARF3, first to cell membranes and then to the nuclear compartment, where ARF3 colocalized with acetylated histone H3 in discrete regions [10].
• However, addition of myristoylated ARF3 (myrARF3) increases the association of arfaptin 1 with the membranes, suggesting that arfaptin 1 and ARF form a complex on the Golgi [11].

Associations of ARF3 with chemical compounds

• In contrast, the NH2 termini of Group I ARFs (ARF1 and ARF3), although fully deformylated, undergo only partial methionine cleavage [12].
• 5. The enzyme was inhibited by oleate and activated by the small G proteins ARF3 and RhoA in the presence of guanosine 5'-3-O-(thio)triphosphate [13].
• In the ARF 3 gene in contrast to those of other GTP-binding proteins, the sequence NKXD (which is thought to contribute to the specificity of interaction with the guanine ring) is divided between exons 4 and 5 [7].

Physical interactions of ARF3

• Golgi incubated with GTP[gamma S] and purified ARF 1 or 3 bound more ARF 1 than ARF 3 [3].
• Further deletion mapping allowed the identification of an 88 amino acid Arf3 binding domain in the C-terminus of MKLP1 [8].

Other interactions of ARF3

• It activated native ARF (mixture of ARF1 and ARF3) more effectively than it did any of the nonmyristoylated recombinant ARFs [14].
• In this study, we define sites of interaction between LTA and human ARF3 [15].
• Neither synergistic interactions between ARF3 and RhoA nor between these G proteins and PKC-alpha or -betaII were observed [13].
• The C-terminal domain of MKLP1 was expressed and purified from bacteria as a GST fusion protein and shown to bind Arf3 in a GTP-dependent fashion [8].
• Isolation and characterization of the human gene for ADP-ribosylation factor 3, a 20-kDa guanine nucleotide-binding protein activator of cholera toxin [7].

Analytical, diagnostic and therapeutic context of ARF3

• Comparative sequence analysis allows us to identify potential regulatory elements for wnt1 and ARF3, which are common to fish and mammals [16].
• Nine mutations in the switch I and switch II regions of human ADP-ribosylation factor 3 (ARF3) were isolated from loss-of-interaction screens, using two-hybrid assays with three different effectors [4].

References