Expression of TAL-1 proteins in human tissues

Abstract

Rearrangement of the tal-1 gene (also known as SCL or TCL-5) occurs in at least 25% of T-cell acute lymphoblastic leukemias (T-ALLs) and results in the aberrant expression of tal-1 mRNA in the neoplastic cells. Also, tal-1 mRNA is constitutively expressed in erythroid precursors and megakaryocytes. This report describes a direct immunocytochemical study of the distribution and localization of TAL-1 protein in normal human tissues and cell lines using four monoclonal antibodies raised against recombinant TAL-1 proteins. One of these reagents recognizes a protein of 41 kD molecular weight in in vitro- translated TAL-1 proteins, two others recognize proteins of 39 and 41 kD molecular weight, and the fourth antibody also recognizes a TAL-1 protein of 22 kD in addition to the 39- and 41-kD proteins. These anti- TAL-1 antibodies label the nuclei of erythroid precursor cells and megakaryocytes in fetal liver and adult bone marrow. The punctate pattern of nuclear labeling suggests that TAL-1 may comprise part of a novel nuclear structure, similar to that recently found for the PML protein. The nuclei of T cell lines known to express mRNA encoding the full-length TAL-1 protein (eg, CCRF-CEM, RPMI 8402, and Jurkat) are also labeled. A study of normal human tissues (including thymus) showed labeling of smooth muscle, some tissue macrophages, and endothelial cells. TAL-1 protein is undetectable in other cell types. These reagents may play an important role in the diagnosis of T-ALL and could also be used in the context of lymphoma diagnosis on routinely fixed material.

Protein dimerization between Lmo2 (Rbtn2) and Tal1 alters thymocyte development and potentiates T cell tumorigenesis in transgenic mice.

“…The same CD2-promoter was used to generate mice expressing Tall (mice herein called CD2-tall). Extracts prepared from transgenic thymocytes were examined by Westem blotting with a monoclonal anti-Tall antibody (Pulford et al, 1995) which preferentially recognizes human rather than mouse Tall protein ( Figure IA). This antibody can therefore distinguish transgenic Tall (whose origin was a human cDNA) from endogenous mouse protein.…”

“…A two-step immunoprecipitation-Westem blotting procedure was used to assess whether Lmo2-Tall dimers were present in transgenic thymocytes. If Tall is associated with Lmo2 in the double transgenic mice, it will be coprecipitated along with Lmo2 by anti-Lmo2 antiserum; co-precipitated Tall protein can then be visualized by Western blotting of the immunoprecipitated material using anti-Tall antibody (Pulford et al, 1995). Equal amounts ,...~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.. .. .... MEL or HEL) or 107 thymocytes of 6-week-old mice, and separated on 12% SDS-PAGE followed by transfer to a nitrocellulose membrane.…”

“…Twenty micrograms of protein were fractionated by 12% SDS-PAGE and transferred to nitrocellulose filters. The filters were washed for 1 h in phosphate-buffered saline with 0.1% Tween 20 and 5% powdered skimmed milk before 1 h incubation with a 1:100 dilution of anti-Tall monoclonal antibody (Pulford et al, 1995). The filters were washed three times, incubated with a 1:10 000 dilution of horseradish peroxidase-conjugated anti-mouse antibody (Amersham) for I h and washed eight times.…”

Loss of TAL-1 protein activity induces premature apoptosis of Jurkat leukemic T cells upon medium depletion.

“…To further characterize this mutant TAL-1 protein, we performed Western blot analysis using several monoclonal antibodies which recognize distinct epitopes along the TAL-1 protein (Pulford et al, 1995). In the parental Jurkat cells, the MAb 2TL136, which reacts with an epitope lying between the Metl60 and Metl76 of TAL-1, revealed one major doublet migrating at 42/44 kDa and a minor one at 39/41 kDa ( Figure 1, lanes 2-3).…”

Chromatin immunoselection defines a TAL-1 target gene

“…Fractions containing nucleoprotein complexes were selected and dialyzed against dialysis buffer (10 mM Tris, 1 mM EDTA, 0.5 mM PMSF, pH 7.5). The pooled selected chromatin fractions were subjected to immunoprecipitation, using the anti-TAL-1 antibody (2TL136 Mab, 10 μg/ml, a gift from D.Mathieu) (Pulford et al, 1995) in the dialysis buffer supplemented with 1% NP-40 for 4 h at 4°C. After addition of protein G Plus-Agarose (Santa Cruz Biotechnology), incubation was continued for an additional 4 h at 4°C.…”