Erythroid-specific, high level expression of the ␤-globin genes is regulated by the locus control region (LCR), composed of multiple DNase I-hypersensitive sites and located far upstream of the genes. Recent studies have shown that LCR core elements recruit RNA polymerase II (pol II). In the present study we demonstrate the following: 1) pol II and other basal transcription factors are recruited to LCR core hypersensitive elements; 2) pol II dissociates from and re-associates with the globin gene locus during replication; 3) pol II interacts with the LCR but not with the ␤-globin gene prior to erythroid differentiation in embryonic stem cells; and 4) the erythroid transcription factor NF-E2 facilitates the transfer of pol II from immobilized LCR constructs to a ␤-globin gene in vitro. The data are consistent with the hypothesis that the LCR serves as the primary attachment site for the recruitment of macromolecular complexes involved in chromatin structure alterations and transcription of the globin genes.The five genes of the human ␤-globin locus are expressed in erythroid cells in a tissue-and developmental stage-specific manner (1). Appropriate expression of the globin genes is regulated by many DNA elements that are located proximal and distal to the genes. The human ␤-globin locus control region (LCR) 1 is a powerful regulatory DNA element located far upstream of the genes and is required for high level expression of all the globin genes throughout development (1, 2). The LCR, unlike classical enhancer elements, operates in an orientationdependent manner (3). There is currently no consensus on how the LCR acts to stimulate globin gene transcription, but it is generally believed that it involves some form of communication between the LCR and the globin genes (4 -6). The LCR is composed of several regions that exhibit extremely high sensitivity to DNase I in erythroid cells (hypersensitive HS sites 1-5). The core HS sites contain clusters of transcription factor binding sites and are separated from each other by 2-4 kbp (2). The results from analyzing human LCR function at ectopic sites in the context of transgenic mice demonstrate that the HS sites synergistically enhance globin gene transcription (7-12), whereas studies in the endogenous murine locus show that the core HS sites function additively (13-15).Recent models view the LCR as a holocomplex in which the individual HS sites interact via extensive protein/DNA and protein/protein interactions (7,16,17). The LCR holocomplex may provide a highly accessible region for the efficient recruitment of macromolecular complexes involved in chromatin modification and transcription (18). Indeed, it has been shown that RNA polymerase II (pol II) is recruited to LCR HS sites in vitro and in vivo (19 -22), suggesting that transcription complexes are first recruited to the LCR and subsequently delivered to the globin genes (18). Sawado et al. (23) recently demonstrated that another important function of the LCR is to regulate transcription elongation at the adult ␤...

The permanent storage of carbon in mineral form using natural brines found in geologic formations is at the forefront of carbon sequestration research. A complex chemistry describes the ultimate fixation of carbon in stable minerals, such as calcite. However, the parameters that govern carbonate formation are not well understood. Accordingly, the purpose of this study is to induce and characterize calcite formation by reacting natural gas brine with CO2. Brine pH has a significant effect on this conversion and can thus be adjusted to induce calcite precipitation using a laboratory scale reactor operated at temperatures of 75 and 150 °C and pressures of 600 and 1500 psi. Initial pH conditions of at least 9.0 are optimal for carbonate precipitation in reactions of 18 h. Although the reaction duration is not long enough to successfully correlate brine compositional changes with precipitation and pH evolution, X-ray diffraction analysis clearly confirms the presence of calcite. Scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis provides an introductory look at the microscale production of these minerals.