Separation of two molecular forms of human estrogen receptor by hydrophobic interaction chromatography. Gradient optimization and tissue comparison

Methods of calculating protein hydrophobicity and their application in developing correlations to predict hydrophobic interaction chromatography retention

Hydrophobic interaction chromatography (HIC) is a key technique for protein separation and purification. Different methodologies to estimate the hydrophobicity of a protein are reviewed, which have been related to the chromatographic behavior of proteins in HIC. These methodologies consider either knowledge of the three-dimensional structure or the amino acid composition of proteins. Despite some restrictions; they have proven to be useful in predicting protein retention time in HIC.

Expression of estrogen receptor variants in normal and neoplastic human uterus

Estrogen receptor variants lacking internal exons and representing dominant positive and negative activity may be involved in the initiation and/or progression of endocrine dependent tumors. To assess the role of estrogen receptor in uterine disease, we have analyzed both normal and neoplastic uterine samples for the presence of variant estrogen receptors using the sensitive technique of RT-PCR and direct automated DNA sequencing of the amplified products. Our analysis was conducted to determine the presence of spliced variants lacking exons 3 through exon 8. We demonstrate that both the normal and neoplastic human uterus contains a number of spliced variants of the estrogen receptor that co-exist with the wild type receptor. Variants lacking exons 4, 5 and 7 but not exons 3 and 6 were detected. Also, a novel partial deletion in exon 8 was detected in both the normal and neoplastic tissues, although a total deletion of this exon was not observed. In addition another region of exon 8 deletion was found to be present in one tumor tissue which also contained an insertion within this region, however, other tumors did not contain this variant. In addition, double exon deletion variants were observed lacking exons 3 and 4, exons 4 and 5, and exon 7 with part of exon 8. Although our data represents a limited number of samples it suggests that splicing of the estrogen receptor message occurs in the normal physiological setting. There does not appear to be any association between the presence or absence of spliced variants of estrogen receptor and uterine tumor formation at the mRNA level.

Detection of two high molecular weight hydrophobic forms of the human estrogen receptor

The human estrogen receptor gene encodes a single protein of molecular weight 65,000 daltons. However, using a sensitive and rapid technique of high-performance hydrophobic interaction chromatography we have detected two distinct estrogen receptor species both of which are high molecular weight proteins (ca. 60A) as determined by high-performance size-exclusion chromatography. These are detected either in the presence or absence of sodium molybdate; rechromatography of individual isoform indicates that the two protein complexes have independent hydrophobic contact points. Consistent elution patterns of the two receptor species indicates they are formed selectively. We conclude that different post-translational modifications of the estrogen receptor protein could allow their specific interaction with non-receptor components resulting in the formation of two distinct high molecular weight complexes which would be rapidly resolved by high-performance hydrophobic interaction chromatography.