The protein product of the het-s heterokaryon incompatibility gene of the fungus Podospora anserina behaves as a prion analog

The het-s locus of Podospora anserina is a heterokaryon incompatibility locus. The coexpression of the antagonistic het-s and het-S alleles triggers a lethal reaction that prevents the formation of viable heterokaryons. Strains that contain the het-s allele can display two different phenotypes, [Het-s] or [Het-s*], according to their reactivity in incompatibility. The detection in these phenotypically distinct strains of a protein expressed from the het-s gene indicates that the difference in reactivity depends on a posttranslational difference between two forms of the polypeptide encoded by the het-s gene. This posttranslational modification does not affect the electrophoretic mobility of the protein in SDS/PAGE. Several results suggest a similarity of behavior between the protein encoded by the het-s gene and prions. The [Het-s] character can propagate in [Het-s*] strains as an infectious agent, producing a [Het-s*] --> [Het-s] transition, independently of protein synthesis. Expression of the [Het-s] character requires a functional het-s gene. The protein present in [Het-s] strains is more resistant to proteinase K than that present in [Het-s*] mycelium. Furthermore, overexpression of the het-s gene increases the frequency of the transition from [Het-s*] to [Het-s]. We propose that this transition is the consequence of a self-propagating conformational modification of the protein mediated by the formation of complexes between the two different forms of the polypeptide.     

Low phase noise IP VCO for multistandard communication using a 0.35-/spl mu/m BiCMOS SiGe technology

In this letter, we report that a commonly used 0.35-/spl mu/m, 60-GHz-F/sub MAX/ BiCMOS SiGe monolithic microwave integrated circuit (MMIC) technology is able to provide very low phase noise signal generation in the X-band frequency range. This statement has been demonstrated using a differential LC voltage-controlled oscillator (VCO) in which varactors are realized with metal-oxide semiconductor (MOS) transistors and inductors with a patterned ground shield technology. This VCO features an output power signal in the range of -5 dBm and exhibits a phase noise of -96 dBc/Hz at a frequency offset of 100kHz from carrier and -120 dBc/Hz at a frequency offset of 1 MHz. The VCO features a tuning range of 430 MHz or 4.3% of its operating frequency. Its power consumption is in the range of 70 mW (200 mW with buffers circuits) for a chip size of 800/spl times/1000 /spl mu/m/sup 2/ (including RF probe pads).