Patrick S. McCaw

Bio: Patrick S. McCaw is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Spliceosome & SR protein. The author has an hindex of 6, co-authored 6 publications receiving 4359 citations.

The gene for enhancer binding proteins E12/E47 lies at the t(1;19) breakpoint in acute leukemias.

Abstract: The gene (E2A) that codes for proteins with the properties of immunoglobulin enhancer binding factors E12/E47 was mapped to chromosome region 19p13.2-p13.3, a site associated with nonrandom translocations in acute lymphoblastic leukemias. The majority of t(1;19)(q23;p13)-carrying leukemias and cell lines studied contained rearrangements of E2A as determined by DNA blot analyses. The rearrangements altered the E2A transcriptional unit, resulting in the synthesis of a transcript larger than the normal-sized E2A mRNAs in one of the cell lines with this translocation. These observations indicate that the gene for a transcription factor is located at the breakpoint of a consistently recurring chromosomal translocation in many acute leukemias and suggest a direct role for alteration of such factors in the pathogenesis of some malignancies.

New proteins related to the Ser-Arg family of splicing factors.

Abstract: A family of six highly conserved proteins that contain domains rich in alternating serine/arginine residues (SR proteins) function in the regulation of splice site selection and are required for splicing. Using a selective precipitation method, more than 35 proteins were detected in nuclear extracts of HeLa cells that co-fractionate with the defined SR family. Many of these proteins were recognized by three monoclonal antibodies that bind to distinct phosphoepitopes on SR proteins. Two of these SR-related proteins were identified as the nuclear matrix antigens B1C8 and B4A11, which previously have been implicated in splicing. A subset of SR proteins, in their phosphorylated state, are associated with spliceosome complexes through both steps of the splicing reaction, remaining preferentially bound to complexes containing the exon-product. In contrast, other SR-related proteins appear to remain specifically associated with the intron-Iariat complex. The results indicate the existence of a potentially large group of SR-related proteins, and also suggest possible additional functions of SR proteins at a post-splicing level.

SC35-mediated reconstitution of splicing in U2AF-depleted nuclear extract

Abstract: Assembly of the mammalian spliceosome is known to proceed in an ordered fashion through several discrete complexes, but the mechanism of this assembly process may not be universal. In an early step, pre-mRNAs are committed to the splicing pathway through association with U1 small nuclear ribonucleoprotein (snRNP) and non-snRNP splicing factors, including U2AF and members of the SR protein family. As a means of studying the steps of spliceosome assembly, we have prepared HeLa nuclear extracts specifically depleted of the splicing factor U2AF. Surprisingly, the SR protein SC35 can functionally substitute for U2AF65 in the reconstitution of pre-mRNA splicing in U2AF-depleted extracts. This reconstitution is substrate-specific and is reminiscent of the SC35-mediated reconstitution of splicing in extracts depleted of U1 snRNP. However, SC35 reconstitution of splicing in U2AF-depleted extracts is dependent on the presence of functional U1 snRNP. These observations suggest that there are at least three distinguishable mechanisms for the binding of U2 snRNP to the pre-mRNA, including U2AF-dependent and -independent pathways.

NeuN, a neuronal specific nuclear protein in vertebrates.

Abstract: A battery of monoclonal antibodies (mAbs) against brain cell nuclei has been generated by repeated immunizations. One of these, mAb A60, recognizes a vertebrate nervous system- and neuron-specific nuclear protein that we have named NeuN (Neuronal Nuclei). The expression of NeuN is observed in most neuronal cell types throughout the nervous system of adult mice. However, some major cell types appear devoid of immunoreactivity including cerebellar Purkinje cells, olfactory bulb mitral cells, and retinal photoreceptor cells. NeuN can also be detected in neurons in primary cerebellar cultures and in retinoic acid-stimulated P19 embryonal carcinoma cells. Immunohistochemically detectable NeuN protein first appears at developmental timepoints which correspond with the withdrawal of the neuron from the cell cycle and/or with the initiation of terminal differentiation of the neuron. NeuN is a soluble nuclear protein, appears as 3 bands (46-48 × 10(3) M(r)) on immunoblots, and binds to DNA in vitro. The mAb crossreacts immunohistochemically with nervous tissue from rats, chicks, humans, and salamanders. This mAb and the protein recognized by it serve as an excellent marker for neurons in the central and peripheral nervous systems in both the embryo and adult, and the protein may be important in the determination of neuronal phenotype.