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In III–V IC processing, lift-off patterning is universally used. Historically used negative resist has its limitations; hence the image reverse process using positive tone resist has been utilized as the main work horse in lift-off applications. Metal lift-off processes using a specially designed chemically amplified (CAMP) negative tone resist have been evaluated for thin and thick metal layers to have a varying degree of success. Lift-off using CAMP photoresists has made it possible to reduce cycle time (~57% reduction in $1\times$ theoretical cycle time per layer) and reduce cost (due to elimination of steps) as compared to the image reverse process. However, achieving consistent lift-off and critical dimension (CD) control presents challenges, which are discussed in this paper. [ABSTRACT FROM AUTHOR]

The objective of this paper is to find a sequence of jobs for the permutation flow shop to minimise the makespan. The shop consists of 10 machines. A feed-forward back-propagation artificial neural network (ANN) is used to solve the problem. The network is trained with the optimal sequences for five-, six- and seven-job problems. This trained network is then used to solve a problem with a greater number of jobs. The sequence obtained using the neural network is used to generate the initial population for the genetic algorithm (GA) using the random insertion perturbation scheme (RIPS). The makespan of the sequence obtained by this approach (ANN-GA-RIPS) is compared with that obtained using GA starting with a random population (ANN-GA). It was found that the ANN-GA-RIPS approach performs better than ANN-GA starting with a random population. The results obtained are compared with those obtained using the Nawaz, Enscore and Ham (NEH) heuristic and upper bounds of Taillard's benchmark problems. ANN-GA-RIPS performs better than the NEH heuristic and the results are found to be within 5% of the upper bounds. [ABSTRACT FROM AUTHOR]

In this paper, the evolution of various lithographic processes aimed at fabricating robust tantalum nitride (TaN) resistors in GaAs-based BiFET and BiHEMT technologies are discussed in detail. Such approaches include the common image reverse photograph process (via amine poisoning) using a positive tone resist, the use of a chemically amplified negative tone resist, and also straight patterning of a positive tone resist. The aforementioned approaches were found to have their own unique challenges as it applied to printing robust TaN-based resistors approaching nearly a micron in width which is needed for high density mixed signal designs. We will explore many of these challenges in detail for the various lithography schemes. [ABSTRACT FROM AUTHOR]

T-cell polarization is required for cell migration and cell-cell inter- actions, cellular behaviors crucial for lymphocyte differentiation. Despite expression of the epithelial polarity network in T cells, neither its contribution to thymocyte polarity nor its requirement during development is known. We report here that depletion of the polarity protein Scribble in hematopoietic progenitor cells results in inefficient T-cell development characterized by a partial developmental block during the early double-negative (DN) stage of differentiation. Scribble-depleted hematopoietic progenitor cells exhibit a delayed transition into late CD44lo/-CD25+ DN3 cells, evidenced by the accumulation of early CD44intCD25+ DN3 cells. As a consequence, a limited cellular expansion and a reduced frequency of intracellular T-cell receptor β-positive DN3 cells are ob- served among Scribble-deficient differentiating T cells. Moreover, whereas purified Scribble-depleted DN2 and DN3 cells do not ex- hibit compromised spontaneous motility, 1-cell clustering and pro- longed homotypic interactions among such cells are reduced. This deficiency correlates with a lack of polarization of the integrin LFA-1 during 1-cell migration or on the initiation of T-cell-T-cell interactions. Scribble is therefore a critical contributor to the clus- tering of immature T cells, an event shown here to be necessary for efficient developmental progression. [ABSTRACT FROM AUTHOR]

Background: Recombinational systems have been developed to rapidly shuttle Open Reading Frames (ORFs) into multiple expression vectors in order to analyze the large number of cDNAs available in the post-genomic era. In the Creator system, an ORF introduced into a donor vector can be transferred with Cre recombinase to a library of acceptor vectors optimized for different applications. Usability of the Creator system is impacted by the ability to easily manipulate DNA, the number of acceptor vectors for downstream applications, and the level of protein expression from Creator vectors. Results: To date, we have developed over 20 novel acceptor vectors that employ a variety of promoters and epitope tags commonly employed for proteomics applications and gene function analysis. We also made several enhancements to the donor vectors including addition of different multiple cloning sites to allow shuttling from pre-existing vectors and introduction of the lacZ alpha reporter gene to allow for selection. Importantly, in order to ameliorate any effects on protein expression of the loxP site between a 5' tag and ORF, we introduced a splicing event into our expression vectors. The message produced from the resulting 'Creator Splice' vector undergoes splicing in mammalian systems to remove the loxP site. Upon analysis of our Creator Splice constructs, we discovered that protein expression levels were also significantly increased. Conclusion: The development of new donor and acceptor vectors has increased versatility during the cloning process and made this system compatible with a wider variety of downstream applications. The modifications introduced in our Creator Splice system were designed to remove extraneous sequences due to recombination but also aided in downstream analysis by increasing protein expression levels. As a result, we can now employ epitope tags that are detected less efficiently and reduce our assay scale to allow for higher throughput. The Creator Splice system appears to be an extremely useful tool for proteomics. [ABSTRACT FROM AUTHOR]

The polo-like kinase Plk4 (also called Sak) is required for late mitotic progression, cell survival and postgastrulation embryonic development. Here we identified a phenotype resulting from Plk4 haploinsufficiency in Plk4 heterozygous cells and mice. Plk4+/− embryonic fibroblasts had increased centrosomal amplification, multipolar spindle formation and aneuploidy compared with wild-type cells. The incidence of spontaneous liver and lung cancers was ∼15 times high in elderly Plk4+/− mice than in Plk4+/+ littermates. Using the in vivo model of partial hepatectomy to induce synchronous cell cycle entry, we determined that the precise regulation of cyclins D1, E and B1 and of Cdk1 was impaired in Plk4+/− regenerating liver, and p53 activation and p21 and BubR1 expression were suppressed. These defects were associated with progressive cell cycle delays, increased spindle irregularities and accelerated hepatocellular carcinogenesis in Plk4+/− mice. Loss of heterozygosity occurs frequently (∼60%) at polymorphic markers adjacent to the PLK4 locus in human hepatoma. Reduced Plk4 gene dosage increases the probability of mitotic errors and cancer development. [ABSTRACT FROM AUTHOR]

Rho GTPases regulate reorganization of actin and microtubule cytoskeletal structures during both interphase and mitosis. The timing and subcellular compartment in which Rho GTPases are activated is controlled by the large family of Rho GTP exchange factors (RhoGEFs). Here, we show that the microtubule-associated RhoGEF Lfc is required for the formation of the mitotic spindle during prophase/prometaphase The inability of cells to assemble a functioning spindle after Lfc inhibition resulted in a delay in mitosis and an accumulation of prometaphase cells. Inhibition of Lfc's primary target Rho GTPase during Prophase/prometaphase, or expression of a catalytically inactive mutant of Lfc, also prevented normal spindle assembly and resulted in delays in mitotic progression. Coinjection of constitutively active Rho GTPase rescued the spindle defects caused by Lfc inhibition, suggesting the requirement of RhoGTP in regulating spindle assembly. Lastly, we implicate mDia1 as an important effector of Lfc signaling. These findings demonstrate a role for Lfc, Rho, and mDia1 during mitosis. [ABSTRACT FROM AUTHOR]

TMF/ARA160 is a Golgi resident protein whose cellular functions have not been conclusively revealed. Herein we show that TMF/ARA160 can direct the proteasomal degradation of the key cell growth regulator-Stat3. TMF/ARA160 was dispersed in the cytoplasm of myogenic C2C12 cells that were grown under low-serum conditions. The cytoplasmic distribution of TMF/ARA160 was accompanied by its transient association with the tyrosine kinase Fer and with Stat3, which underwent proteasomal degradation under those conditions. Moreover, serum deprivation induced the association of ubiquitinated proteins, with the TMF/ARA160 complex. However, TMF/ARA160 did not bind Stat1, whose cellular levels were increased in serum-starved C2C12 cells. Amino-acid sequence analysis identified a BC-box element in TMF/ARA160 that mediated the binding of this protein to elongin C. Ectopic expression of TMF/ARA160 in serum-starved C2C12 cells drove the ubiquitination and proteasomal degradation of Stat3, an effect that was not caused by TMF/ARA160 devoid of the BC-box motif. Thus, the Golgi apparatus harbors a novel BC-box-containing protein that can direct Stat3 to proteasomal degradation. Interestingly, the level of TMF/ARA160 was significantly decreased in malignant brain tumors, implying a suppressive role of that protein in tumor progression.Oncogene (2004) 23, 8908-8919. doi:10.1038/sj.onc.1208149 Published online 4 October 2004 [ABSTRACT FROM AUTHOR]

The human transcription factor CA150 modulates human immunodeficiency virus type 1 gene transcription and contains numerous signaling elements, including six FF domains. Repeated FF domains are present in several transcription and splicing factors and can recognize phosphoserine motifs in the C-terminal domain (CTD) of RNA polymerase II (RNAPII). Using mass spectrometry, we identify a number of nuclear binding partners for the CA150 FF domains and demonstrate a direct interaction between CA150 and Tat-SF1, a protein involved in the coupling of splicing and transcription. CA150 FF domains recognize multiple sites within the Tat-SF1 protein conforming to the consensus motif (D/E)2/5-F/W/Y-(D/E)2/5. Individual FF domains are capable of interacting with Tat-SF1 peptide ligands in an equivalent and noncooperative manner, with affinities ranging from 150 to 500 μM. Repeated FF domains therefore appear to bind their targets through multiple weak interactions with motifs comprised of negatively charged residues flanking aromatic amino acids. The RNAPII CTD represents a consensus FF domain-binding site, contingent on generation of the requisite negative charges by phosphorylation of serines 2 and 5. We propose that CA150, through the dual recognition of acidic motifs in proteins such as Tat-SF1 and the phosphorylated CTD, could mediate the recruitment of transcription and splicing factors to actively transcribing RNAPII. [ABSTRACT FROM AUTHOR]

The evolutionarily conserved proteins Par-6, atypical protein kinase C (aPKC), Cdc42 and Par-3 associate to regulate cell polarity and asymmetric cell division, but the downstream targets of this complex are largely unknown. Here we identify direct physiological interactions between mammalian aPKC, murine Par-6C (mPar-6C) and Mlgl, the mammalian orthologue of the Drosophila melanogaster tumour suppressor Lethal (2) giant larvae. In cultured cell lines and in mouse brain, aPKC, mPar-6C and Mlgl form a multiprotein complex in which Mlgl is targeted for phosphorylation on conserved serine residues. These phosphorylation sites are important for embryonic fibroblasts to polarize correctly in response to wounding and may regulate the ability of Mlgl to direct protein trafficking. Our data provide a direct physical and regulatory link between proteins of distinct polarity complexes, identify Mlgl as a functional substrate for aPKC in cell polarization and indicate that aPKC is directed to cell polarity substrates through a network of protein-protein interactions. [ABSTRACT FROM AUTHOR]

The tyrosine phosphatase Shp2 is recruited into tyrosine-kinase signalling pathways through binding of its two amino-terminal SH2 domains to specific phosphotyrosine motifs, concurrent with its re-localization and stimulation of phosphatase activity. Shp2 can potentiate signalling through the MAP-kinase pathway and is required during early mouse development for gastrulation. Chimaeric analysis can identify, by study of phenotypically normal embryos, tissues that tolerate mutant cells (and therefore do not require the mutated gene) or lack mutant cells (and presumably require the mutated gene during their developmental history). We therefore generated chimaeric mouse embryos to explore the cellular requirements for Shp2. This analysis revealed an obligatory role for Shp2 during outgrowth of the limb. Shp2 is specifically required in mesenchyme cells of the progress zone (PZ), directly beneath the distal ectoderm of the limb bud. Comparison of Ptpn11 (encoding Shp2)-mutant and Fgfr1 (encoding fibroblast growth factor receptor-1)-mutant chimaeric limbs indicated that in both cases mutant cells fail to contribute to the PZ of phenotypically normal chimaeras, leading to the hypothesis that a signal transduction pathway, initiated by Fgfr1 and acting through Shp2, is essential within PZ cells. Rather than integrating proliferative signals, Shp2 probably exerts its effects on limb development by influencing cell shape, movement or adhesion. Furthermore, the branchial arches, which also use Fgfs during bud outgrowth, similarly require Shp2. Thus, Shp2 regulates phosphotyrosine-signalling events during the complex ectodermal-mesenchymal interactions that regulate mammalian budding morphogenesis. [ABSTRACT FROM AUTHOR]

The abstract in is incorrect. The word “photograph” was used in error rather than the more correct, “photo.” The abstract should read: In this paper, the evolution of various lithographic processes aimed at fabricating robust tantalum nitride (TaN) resistors in GaAs-based BiFET and BiHEMT technologies are discussed in detail. Such approaches include the common image reverse photo process (via amine poisoning) using a positive tone resist, the use of a chemically amplified negative tone resist, and also straight patterning of a positive tone resist. The aforementioned approaches were found to have their own unique challenges as it applied to printing robust TaN-based resistors approaching nearly a micron in width which is needed for high density mixed signal designs. We will explore many of these challenges in detail for the various lithography schemes. [ABSTRACT FROM AUTHOR]