DESCRIPTION

USF2 (upstream stimulating factor 2) is a widely expressed basic helical-loop-helical transcription factor that often forms a heterodimer with USF1 and recognizes the E-box sequence (CACGTG) in the promoter of target genes. It participates in the regulation of glucose and lipid metabolism, cell cycle and immune response-related gene expression, plays an important role in tissues such as the liver and pancreas, and is associated with metabolic diseases and tumor development.

PRINCIPLE OF THE ASSAY

An anti-tag antibody is pre-coated onto the bottom of wells. After adding antigen or samples, Tagged-Capture antibody and HRP-conjugated detection antibody, a sandwich complex is formed in the solution. TMB acts as a HRP substrate, and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns the solution yellow. The color intensity is proportional to the quantity of bound protein, which is measurable at 450 nm with the correction wavelength set at 630 nm.

PRECISION

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested 8 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 16 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	8	2,616.5	48.6	1.9
2	8	676.1	17.3	2.6
3	8	349.6	8.6	2.5

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	2,619.2	56.9	2.2
2	16	677.7	17.5	2.6
3	16	351.4	8.7	2.5

RECOVERY

The recovery of human USF2 spiked to three different levels throughout the range of the assay in cell lysate was evaluated.

Sample Type		Average% of Expected	Range (%)
Cell lysate	1:256	84	73-98
	1:512	89	83-101

LINEARITY

To assess the linearity of the assay, samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay. (The cell lysate was initially diluted 1:32.)

		Cell lysate
1:2	Average% of Expected	100
	Range (%)	-
1:4	Average% of Expected	96
	Range (%)	86-107
1:8	Average% of Expected	91
	Range (%)	90-91
1:16	Average% of Expected	106
	Range (%)	95-117

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Human USF2 One-Step ELISA Kit produced at Sunlong Medical™.