We study a two-user Gaussian Z-interference channel in which only one-sided interference exists. We assume that there is a one-sided conferencing link from the interfering transmitter to the other, which can be used to mitigate the interference. We propose a cooperative transmission scheme that delivers a part of the interfering message through the conferencing link and then applies the dirty paper coding by regarding the delivered message as a known transmit side information. We characterize its achievable rate region for general channel coefficients and show that a finite-rate conferencing can improve both achievable rate region and its sum rate.