David Baltimore

Bio: David Baltimore is an academic researcher from California Institute of Technology. The author has contributed to research in topics: RNA & Virus. The author has an hindex of 203, co-authored 876 publications receiving 162955 citations. Previous affiliations of David Baltimore include Thomas Jefferson University & Johns Hopkins University.

Expression of Animal Virus Genomes

Abstract: The world of animal viruses appears to offer an unfathomable diversity of specimens but, as the molecular biology of the replication of many viruses has been studied, a pattern of behavior has emerged. The viruses can be divided into classes, each of which has its own method of transmitting its genetic information from one generation to the next and its own style of expressing its genetic information. Although in some cases the data are still fragmentary it is possible to outline the behavior of these systems and to place them in a formal scheme. In this paper I will present such a scheme and I will discuss in some detail the behavior of three viral systems which have been investigated in my laboratory. Furthermore, I will discuss some of the implications of the existence of these viral systems in the context of the behavior of normal cells.

Activation of Apoptosis Signal-Regulating Kinase 1 (ASK1) by the Adapter Protein Daxx

Abstract: The Fas death receptor can activate the Jun NH2-terminal kinase (JNK) pathway through the receptor-associated protein Daxx. Daxx was found to activate the JNK kinase kinase ASK1, and overexpression of a kinase-deficient ASK1 mutant inhibited Fas- and Daxx-induced apoptosis and JNK activation. Fas activation induced Daxx to interact with ASK1, which consequently relieved an inhibitory intramolecular interaction between the amino- and carboxyl-termini of ASK1, activating its kinase activity. The Daxx-ASK1 connection completes a signaling pathway from a cell surface death receptor to kinase cascades that modulate nuclear transcription factors.

Preferential utilization of the most JH-proximal VH gene segments in pre-B-cell lines.

Abstract: The most JH-proximal VH gene segments are used highly preferentially to form VHDJH rearrangements in pre-B-cell lines. This result demonstrates that the rate at which immunoglobulin VH gene segments recombine is influenced by their chromosomal organization, and that the initial repertoire ofVH genes expressed in pre-B cells is strikingly different from that seen in mature populations.

Transformation of an interleukin 3-dependent hematopoietic cell line by the chronic myelogenous leukemia-specific P210bcr/abl protein

Abstract: The P210bcr/abl protein is associated with virtually every case of human chronic myelogenous leukemia. Unlike the related P160gag/v-abl oncogene product of Abelson murine leukemia virus, P210bcr/abl does not transform NIH 3T3 fibroblasts. To assess whether P210bcr/abl might transform hematopoietic cell types, retroviral constructs encoding P210bcr/abl were used to infect the bone marrow-derived interleukin 3-dependent Ba/F3 cell line. As for P160gag/v-abl, cell lines expressing P210bcr/abl were growth factor independent and tumorigenic in nude mice. No evidence for autocrine production of interleukin 3 by factor-independent cell lines was found. These experiments establish that P210bcr/abl can transform hematopoietic cell types to tumorigenicity.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Multiplex Genome Engineering Using CRISPR/Cas Systems

Abstract: Functional elucidation of causal genetic variants and elements requires precise genome editing technologies. The type II prokaryotic CRISPR (clustered regularly interspaced short palindromic repeats)/Cas adaptive immune system has been shown to facilitate RNA-guided site-specific DNA cleavage. We engineered two different type II CRISPR/Cas systems and demonstrate that Cas9 nucleases can be directed by short RNAs to induce precise cleavage at endogenous genomic loci in human and mouse cells. Cas9 can also be converted into a nicking enzyme to facilitate homology-directed repair with minimal mutagenic activity. Lastly, multiple guide sequences can be encoded into a single CRISPR array to enable simultaneous editing of several sites within the mammalian genome, demonstrating easy programmability and wide applicability of the RNA-guided nuclease technology.

Activating mutations in the epidermal growth factor receptor underlying responsiveness of non-small-cell lung cancer to gefitinib

Abstract: BACKGROUND Most patients with non-small-cell lung cancer have no response to the tyrosine kinase inhibitor gefitinib, which targets the epidermal growth factor receptor (EGFR). However, about 10 percent of patients have a rapid and often dramatic clinical response. The molecular mechanisms underlying sensitivity to gefitinib are unknown. METHODS We searched for mutations in the EGFR gene in primary tumors from patients with non-small-cell lung cancer who had a response to gefitinib, those who did not have a response, and those who had not been exposed to gefitinib. The functional consequences of identified mutations were evaluated after the mutant proteins were expressed in cultured cells. RESULTS Somatic mutations were identified in the tyrosine kinase domain of the EGFR gene in eight of nine patients with gefitinib-responsive lung cancer, as compared with none of the seven patients with no response (P<0.001). Mutations were either small, in-frame deletions or amino acid substitutions clustered around the ATP-binding pocket of the tyrosine kinase domain. Similar mutations were detected in tumors from 2 of 25 patients with primary non-small-cell lung cancer who had not been exposed to gefitinib (8 percent). All mutations were heterozygous, and identical mutations were observed in multiple patients, suggesting an additive specific gain of function. In vitro, EGFR mutants demonstrated enhanced tyrosine kinase activity in response to epidermal growth factor and increased sensitivity to inhibition by gefitinib. CONCLUSIONS A subgroup of patients with non-small-cell lung cancer have specific mutations in the EGFR gene, which correlate with clinical responsiveness to the tyrosine kinase inhibitor gefitinib. These mutations lead to increased growth factor signaling and confer susceptibility to the inhibitor. Screening for such mutations in lung cancers may identify patients who will have a response to gefitinib.

Multiplex Genome Engineering Using CRISPR/Cas Systems

Abstract: Genome Editing Clustered regularly interspaced short palindromic repeats (CRISPR) function as part of an adaptive immune system in a range of prokaryotes: Invading phage and plasmid DNA is targeted for cleavage by complementary CRISPR RNAs (crRNAs) bound to a CRISPR-associated endonuclease (see the Perspective by van der Oost). Cong et al. (p. 819, published online 3 January) and Mali et al. (p. 823, published online 3 January) adapted this defense system to function as a genome editing tool in eukaryotic cells. A bacterial genome defense system is adapted to function as a genome-editing tool in mammalian cells. [Also see Perspective by van der Oost] Functional elucidation of causal genetic variants and elements requires precise genome editing technologies. The type II prokaryotic CRISPR (clustered regularly interspaced short palindromic repeats)/Cas adaptive immune system has been shown to facilitate RNA-guided site-specific DNA cleavage. We engineered two different type II CRISPR/Cas systems and demonstrate that Cas9 nucleases can be directed by short RNAs to induce precise cleavage at endogenous genomic loci in human and mouse cells. Cas9 can also be converted into a nicking enzyme to facilitate homology-directed repair with minimal mutagenic activity. Lastly, multiple guide sequences can be encoded into a single CRISPR array to enable simultaneous editing of several sites within the mammalian genome, demonstrating easy programmability and wide applicability of the RNA-guided nuclease technology.

Translating the Histone Code

Abstract: Chromatin, the physiological template of all eukaryotic genetic information, is subject to a diverse array of posttranslational modifications that largely impinge on histone amino termini, thereby regulating access to the underlying DNA. Distinct histone amino-terminal modifications can generate synergistic or antagonistic interaction affinities for chromatin-associated proteins, which in turn dictate dynamic transitions between transcriptionally active or transcriptionally silent chromatin states. The combinatorial nature of histone amino-terminal modifications thus reveals a “histone code” that considerably extends the information potential of the genetic code. We propose that this epigenetic marking system represents a fundamental regulatory mechanism that has an impact on most, if not all, chromatin-templated processes, with far-reaching consequences for cell fate decisions and both normal and pathological development.