Immunoglobulin motif DNA recognition and heterodimerization of the PEBP2/CBF Runt domain.

The polyomavirus enhancer binding protein 2 (PEBP2) or core binding factor (CBF) is a heterodimeric enhancer binding protein that is associated with genetic regulation of hematopoiesis and osteogenesis. Aberrant forms of PEBP2/CBF are implicated in the cause of the acute human leukemias and in a disorder of bone development known as cleidocranial dysplasia. The common denominator in the natural and mutant forms of this protein is a highly conserved domain of PEBP2/CBF alpha, termed the Runt domain (RD), which is responsible for both DNA binding and heterodimerization with the beta subunit of PEBP2/CBF. The three-dimensional structure of the RD bound to DNA has been determined to be an S-type immunoglobulin fold, establishing a structural relationship between the RD and the core DNA binding domains of NF-kappaB, NFAT1, p53 and the STAT proteins. NMR spectroscopy of a 43.6 kD RD-beta-DNA ternary complex identified the surface of the RD in contact with the beta subunit, suggesting a mechanism for the enhancement of RD DNA binding by beta. Analysis of leukemogenic mutants within the RD provides molecular insights into the role of this factor in leukemogenesis and cleidocranial dysplasia.     

PEBP2/CBF, the murine homolog of the human myeloid AML1 and PEBP2 beta/CBF beta proto-oncoproteins, regulates the murine myeloperoxidase and neutrophil elastase genes in immature myeloid cells.

The myeloperoxidase (MPO) and neutrophil elastase genes are expressed specifically in immature myeloid cells. The integrity of a polyomavirus enhancer core sequence, 5'-AACCACA-3', is critical to the activity of the murine MPO proximal enhancer. This element binds two species, myeloid nuclear factors 1 alpha and 1 beta (MyNF1 alpha and -beta), present in 32D cl3 myeloid cell nuclear extracts. The levels of the MyNF1s increase during early 32D cl3 cell granulocytic differentiation. Both MyNF1 alpha and -beta supershift with an antiserum raised by using a peptide derived from the N terminus of polyomavirus enhancer-binding protein 2/core-binding factor (PEBP2/CBF) alpha subunit. The specific peptide inhibits these supershifts. In vitro-translated PEBP2/CBF DNA-binding domain binds the murine MPO PEBP2/CBF site. An alternate PEBP2/CBF consensus site, 5'-GACCGCA-3', but not a simian virus 40 enhancer core sequence, 5'-TTCCACA-3', binds the MyNF1s in vitro and activates a minimal murine MPO-thymidine kinase promoter in vivo. The murine neutrophil elastase gene 100-bp 5'-flanking sequences contain several functional elements, including potential binding sites for PU.1, C/EBP, c-Myb, and PEBP2/CBF. The functional element 5'-GGCCACA-3' located at positions -66 to 72 differs from the PEBP2/CBF consensus (5'-PuACCPuCA-3') only by an A-to-G transition at position 2. This DNA element binds MyNF1 alpha and -beta weakly. The N terminis of two PEBP2/CBF alpha subunit family members, PEBP2 alpha A and PEBP2 alpha B (murine AML1), are nearly identical, and 32D c13 cl3 cells contain both corresponding mRNAs. Since t(8;21), t(3;21), and inv(16), associated with myeloid leukemias, disrupt subunits of PEBP2/CBF, we speculate that the resulting oncoproteins, AML1-ETO, AML1-EAP, AML1-Evi1, and CBF beta-MYH11, inhibit early myeloid differentiation.     

根癌农杆菌介导转录因子CBF1基因对草莓的转化

以草莓(Fragaria ananassa Duch)品种“达斯莱克特“(Darselect)为试材,用根癌农杆菌介导的方法,将转录因子CBF1基因导入草莓叶盘细胞,经多次筛选获得了转基因植株.转化植株经PCR检测,证实了CBF1基因已经整合到草莓的基因组中.以电解质渗透法检测了植株的抗寒性,结果显示转基因草莓的抗寒能力较未转化植株有明显提高,且不同转基因株系之间提高程度有着差异.     

Identification of a hydrophobic region in the carboxyl terminus of the platelet-derived growth factor beta-receptor which is important for ligand-mediated endocytosis.

The functional properties of carboxyl terminally truncated mutants of the platelet-derived growth factor beta-receptor were compared with those of the wild-type receptor and a receptor mutant made kinase negative by a point mutation. A mutant in which 98 amino acids were deleted retained kinase activity and mediated a mitogenic signal, whereas deletion of 141 or 155 amino acids led to loss of kinase activity and ability to mediate a mitogenic signal. The mutant with 155 amino acids deleted, i.e. the entire carboxyl-terminal tail downstream of the kinase domain, did not undergo ligand-mediated internalization and down-regulation, whereas the mutant with 141 amino acids deleted was internalized at a relatively high rate. This indicates that the 14 amino acids immediately downstream of the kinase domain is of importance for the internalization of the platelet-derived growth factor beta-receptor. This region is hydrophobic and shares no similarity to other sequences postulated to mediate endocytotic signals.