This paper proposed a fast mode decision algorithm for H.264. It performs SKIP mode test firstly. If the SKIP mode is not suitable for the current MB, it performs 16x16 mode test secondly. If the 16x16 mode is not suitable for the current MB, candidate modes for current MB are inferred from given coded correlated MBs by adopting the information of defined mode subsets. Then bottom-up merging and top-down splitting methods are developed based on spatial correlation of MBs. A partial RDO approach which involved these methods is applied to the candidate modes to make target mode selection. Simulation results demonstrate that the proposed algorithm can achieve up speed up 56.56 % - 81.54 % ratio with a little PSNR loss. Increment in bit requirement is also not much noticeable.

With the rapid development of microprocessor, embedded multimedia products are gradually becoming the mainstream in the market. However, the high coding efficiency enabled by the H.264 video compression standard comes with substantially greater algorithmic complexity as compared to that of existing standards. And this additional complexity results in many difficulties in the implementation and optimization tasks. This paper analyzes the algorithms of the two time-consuming modules of integer transform and motion estimation in H.264. Then optimizes the two modules based on the extended instruction set of C64x/C64x+. Finally, deeply pipelined DSP solutions to two modules are presented in this paper. The experiment results show that optimizing parallel assembly can make the codes more efficient.

Prostaglandins, pleiotropic immune modulators that induce protein kinase A (PKA), inhibit gamma interferon induction of class II major histocompatibility complex (MHC) genes. We show that phosphorylation of CIITA by PKA accounts for this inhibition. Treatment with prostaglandin E or 8-bromo-cyclic AMP or transfection with PKA inhibits the activity of CIITA in both mouse and human monocytic cell lines. This inhibition is independent of other transcription factors for the class II MHC promoter. These same treatments also greatly reduced the induction of class II MHC mRNA by CIITA. PKA phosphorylation sites were identified using site-directed mutagenesis and phosphoamino acid analysis. Phosphorylation at CIITA serines 834 and 1050 accounts for the inhibitory effects of PKA on CIITA-driven class II MHC transcription. This is the first demonstration that the posttranslational modification of CIITA mediates inhibition of class II MHC transcription.

Scaffold molecules interact with multiple effectors to elicit specific signal transduction pathways. CIITA, a non-DNA-binding regulator of class II major histocompatibility complex (MHC) gene transcription, may serve as a transcriptional scaffold. Regulation of the class II MHC promoter by CIITA requires strict spatial-helical arrangements of the X and Y promoter elements. The X element binds RFX (RFX5/RFXANK-RFXB/RFXAP) and CREB, while Y binds NF-Y/CBF (NF-YA, NF-YB, and NF-YC). CIITA interacts with all three. In vivo analysis using both N-terminal and C-terminal deletion constructs identified critical domains of CIITA that are required for interaction with NF-YB, NF-YC, RFX5, RFXANK/RFXB, and CREB. We propose that binding of NF-Y/CBF, RFX, and CREB by CIITA results in a macromolecular complex which allows transcription factors to interact with the class II MHC promoter in a spatially and helically constrained fashion.

Mutating the HLA-A*0201 heavy chain from threonine to lysine at position 134 (T134K) results in a molecule that presents exogenous peptide, but cannot present endogenously derived antigen. This is reflected in diminished cell surface expression and altered intracellular trafficking of T134K. The failure of T134K to present endogenous antigen can be overcome by using an ER targeting sequence, suggesting that the antigen presentation defect is restricted to TAP-dependent peptide loading. The ability of T134K to load peptide in a TAP-dependent manner is dramatically reduced compared with HLA-A*0201. By coimmunoprecipitation there is no detectable association of the T134K molecule with the TAP complex. Thus, T134K selectively affects TAP association and peptide loading, suggesting a requirement for the direct interaction of MHC class I heavy chain and the TAP complex for efficient presentation of endogenous antigen.

NF‐Y binds a CCAAT motif found in many eukaryotic polymerase II‐dependent promoters. In the HLA‐DRA promoter it has been demonstrated that stereo‐specific alignment between this motif and the upstream elements X1 and X2 is required for activation. To study the underlying mechanism for this requirement, a panel of transfected cell lines that maintained integrated, wild‐type and mutant promoters were analyzed by in vivo genomic footprinting. Cell lines harboring a mutated CCAAT element exhibited a loss of interactions at the CCAAT site, as expected, and no transcriptional activity. Most importantly, mutation of the CCAAT sequence nearly abolished in vivo binding at the X1 and X2 sites, while mutations of X1 and X2 had little effect on CCAAT box binding. However, X1 and X2 binding was interdependent. In vitro, X1 binding activities are known to be stabilized by NF‐Y binding. Interaction between NF‐Y and X box binding proteins was demonstrated by reciprocal co‐immunoprecipitation in the absence of DNA and co‐affinity purification in the presence of DNA. Collectively, these studies indicate that occupancy of the CCAAT element represents an early event affecting other protein‐DNA interactions and suggest that NF‐Y stabilizes and interacts with X box factors to mediate this function. These findings may represent a common theme among promoters containing a CCAAT element.