The Google Nexus 4, which is made by LG for Google is not designed to support 4G LTE, although we previously heard that a 4G LTE chip had been found inside the device.
The guys over at the XDA developers, previously managed to get the Google Nexus 4 to run on some 4G LTE networks in Canada, and now it would appear that they have managed to get the device running on 4G LTE with US mobile carrier AT&T in select markets.
The Google Nexus 4 is not designed to offer support for 4G LTE, although the presence of the default hardware from the Optimus G means that the device can be made to run on certain bands, you can find out more information on how this is done over at the XDA Developers.
Source Android Police